can't connect iCloud account in Apple TV

Not intuitive, but documented: HT204915, Two-factor authentication for Apple ID

"What if I use two-factor authentication on a device running older software?

If you use two-factor authentication with devices running older OS versions—like an Apple TV (2nd or 3rd generation)—you might be asked to add your six-digit verification code to the end of your password when signing in. Get your verification code from a trusted device running iOS 9 and later or OS X El Capitan and later, or have it sent to your trusted phone number. Then type your password followed by the six-digit verification code directly into the password field."

It may take too long if you get the code before entering the password. Therefore get a new code after entering the password (do not submit yet), then add that code to the end of the password, then submit.

2 factor authentication is optimized for newer software, when using an older device you aren't going to be prompted for the code and need to add it to the password instead (as documented in the article).

As there is a time limit for the code it is then recommended to request the code after entering the password so as to not exceed that limit. If those steps are not followed or the limit is exceeded then it will loop back or produce an error.

As stated above 2FA is optimized for newer software, in which one will enter the password and then be prompted to enter the code separately.

The article is merely stating that when using an older device you will need to add the code to the end of the password instead.

The error message is simply stating that it was unable to sign in, however if the link provided was found to be of no value then you can give that feedback to Apple

I got the solution from another discussion!

1. Type in your Apple ID password in on the Apple TV
2. On another Apple device, go to Settings —> Apple ID —> Passwords & Security —> Get Verification Code
3. On the Apple TV, type in the 6-digit verification code at the end of your password

Ex: Mypersonalpassword334862

Did you follow my instruction to not clear the code on the device displaying it prior to it being accepted by the Apple TV? I and many others in this thread have experienced if you clear the code from the device displaying it before entering the code and having it accepted by the Apple TV that it will not work. I personally was using iTunes remote on my iPhone and so I was clearing the code from my iPhone so that I could enter it using iTunes remote and I suspect this kind of thing was the issue for others as well. You can enter the code using iTunes remote, but in that case you're going to need to have it displaying on another device (another iPhone, an iPad, a Mac, whatever).

Yeah, like I said, I also tried that recently and found that it still works. When this thread started, that was the only option because the Apple TV 3rd generation would not prompt you for the 6-digit code but that code was required (for accounts with 2-factor authentication turned on) and so you had to enter it appended to the password. However, though you can still do that and it's not a problem to follow that approach, you no longer should have to do that as Apple has updated the Apple TV 3rd generation firmware and at this point after you enter the password (without the 6-digit code) you next will be prompted for the 6-digit code. I have found that with either method, you must keep the 6-digit code visible on the device displaying it while you enter it, submit it, and wait for it to be accepted before you can clear it from the device displaying it.

I had the same issue.

I used ‘Get Verification number’ on my IPhone and used that number. No luck.

So used my iPad for the Verfication number, used the remote app on my iPhone and then typed my password+verification number and it worked.

2FA is optimized for newer software, which the 3rd gen cannot run. It is not going to generate a separate screen for the code, like on newer models, and one has to enter the password and code together. Even if a code was generated you can easily exceed the limit when attempting to enter both at once. You need to request the code and then add it to the password to ensure it goes through.

This time I'm bringing all good news, but with a caveat.

The good news: it appears that Apple has resolved the issue with being unable to access iCloud Photos (and it's possible it was also working at the time of my last post and I just didn't know how to "crack the code," so to speak; read on for more info).

The caveat: you have to go through (or at least I had to go through) a lot of gyrations to get there.

The gyrations:

1. First thing to note is that if you're already logged in, you're probably going to have to log out first. I was finding that in iCloud Photos, the albums would display but the actual photos in them would not. I was not able to figure out any way to resolve this (and yes, I tried rebooting) besides logging out and logging back in.
2. As I posted previously, logging into iCloud on the Apple TV 3rd generation now works the same as it does on other devices. You enter your Apple ID then your password and then you'll have to enter the code that will be displayed on one of the other devices on your account (when doing this, I continue to believe it's important that you not clear the code from the other device first, though I didn't test that this time). After you login, you'll need to go into iCloud Photos Settings; what I care about is iCloud Photo Sharing so in there I turned that on and I made sure Photo Stream was turned off, but you'll need to make whatever choice is right for your circumstance.
3. Immediately after logging in when I went to iCloud Photos and it gave me the "iCloud Unavailable" message. But after waiting several minutes and trying again, I got the "Loading iCloud Photos" message, but it just wouldn't clear.
4. So then I went back into Settings and turned off iCloud Photo Sharing.
5. Then I went back into iCloud Photos. Now, with nothing turned on in settings, it asked if I wanted to turn on iCloud Photos. So I said yes. And then, after telling it no, I didn't want to use Photo Stream as my screensaver, I had to login again. Why? No idea.
6. Then after I logged in, it still told me iCloud was unavailable and there was as problem with my password.
7. So then I tried again and then I got logged in and it took me into iCloud Photos showing My Photo Stream with 0 photos (and of course I have hundreds of photos in my Photo Stream). My shared albums were not displayed. So at least I was in, but it wasn't showing me any photos.
8. So then I went back into Settings and turned off iCloud Photo Sharing.
9. Then I turned iCloud Photo Sharing back on.
10. Then I waited several minutes.
11. Then I went back into iCloud Photos and there were my shared albums (with actual access to the photos, unlike in item #1 on this list).

It's possible these exact steps will not work for you. It's possible that you will have to go through even more gyrations to get this to work. It's also possible you will be able to go through less gyrations to get this to work. The point really is that this process is quite nutty and you have to stick with it and keep trying things.

It's rather frustrating. And to depress you even further, I've found that over the last few months iCloud Photos has frequently and randomly stopped working (that is to say, I've been logged in and able to access photos from a shared album and use them as a screensaver and then that just stops working). I've usually able to get things going again just by rebooting the Apple TVs and though what brought me here to this thread is that this time around that didn't work, hopefully going forward when this breaks again (and given how frequently it's broken in the past, I have to believe it's going to break again), a simple reboot will clear it up because I sure as heck don't want to go through all these gyrations on a regular basis.

Okay, so you still did the old approach of entering your password + the 6-digit code together? Yeah, I had tried that previously and that too worked for me. It shouldn't be necessary to do it that way but at least it does still work.

The key points on this for me are:

1. If you can login without having the code visible, awesome! Go with it, and post about it here!
2. But I couldn't login without having the code visible, so I wanted to share that tidbit to potentially take one challenge out of the equation for people.
3. There's no downside to keeping the 6-digit code visible on the device displaying it while you enter it and submit it on your Apple TV and while Apple subsequently validates it, and since following that approach made all the difference for me and, although they didn't necessarily identify it the same way, I believe it's made all the difference for some others, I argue there's no reason not to try it.

The reason it didn't help you is that you weren't trying to accomplish what I was trying to accomplish. I was trying to get logged for iCloud Photo Sharing. You indicated you're trying to get Home Sharing to work. I can't get that one to work either. Check out the discussion at https://discussions.apple.com/thread/250592472 and you'll see that it's widely acknowledged there that at this time there is no way to successfully login to Home Sharing on an Apple TV 3rd generation using an Apple ID with 2-factor authentication enabled. So unfortunately, neither my approach nor anything else is going to do the trick for you at this time.

That's interesting that you get the same number upon multiple requests for a code on your device. I didn't know it worked that way.

It depends on what you're trying to accomplish. If you want to get iCloud Photo Sharing to work, multiple of us have found that it can be done and if you read through this thread you'll see that I've listed out the series of steps I went through to get it to work. In regards to the piece about getting logged in, I found that it was key for me to have the code visible on the device presenting it all the way through entering it, submitting it, and having it validated by Apple. As discussed previously in this thread, this seems strange, but for me it was critical.

If, however, you're talking about Home Sharing, then check out https://discussions.apple.com/thread/250592472 where you'll see that it's a known issue that at this time there is no way to get Home Sharing to work on 2nd and 3rd generation Apple TVs.

Thanks. I tried it by requesting a code first and entering it with my password and it worked...this time.