I keep trying to sign into iTunes on older Apple TV. I get verification code from phone and then go back to type in password followed by code but keeps saying its incorrect. (Real pain typing in passcode with remote)

If you have an Apple TV (2nd or 3rd generation) and two-factor authentication for your Apple ID, then you may be asked to type your password followed by the six-digit verification code directly into the password field. Additionally, there is a time limit, after which the code becomes invalid.

Try this: First enter the characters of your password (do not submit yet), then manually request a new verification code, then append that code to the password (no spaces or other separating characters), and then submit. That should help you get passed the time limit.

I'm having the same issue with an iPadAir (2013). I updated the iOS last night, and now I need to update my Square app. Every time it asks me to sign in it tells me my password is incorrect. I've reset it twice and it accepts none of my new codes. At this point I can't take payments through Square anymore after the required update.

Same