WIFI Password is incorrect: Error Message -3900

Hi there Thruss,

It sounds like you have tried few things already, but there may be some additional steps we can take. If you haven't restored the device by plugging it into iTunes, you may want to try that. Take a look at the section "If your Apple TV still does not respond..."

Apple TV (2nd and 3rd generation): Restoring your Apple TV

http://support.apple.com/kb/HT4367

If the issues persist, then you may want to verify the security settings on your wireless router. The article below has more information.

iOS and OS X: Recommended settings for Wi-Fi routers and access points

http://support.apple.com/kb/HT4199

-Griff W.

I have absolutely same problem simultaneously with 2 Apple TV devices

Suddenly they stopped connecting to the wifi (while connecting to the ethernet OK). I have managed to restore and update software, both via ethernet while connected to TV and also via itunes as suggested above.

However both devices when attempting connection to the wifi respond that password is incorrect (~3900). There is no suggestion to re-enter the password. I tried to connect to other networks available - in this case devices request password alright, but they respond with different error - 100, to the wrong password in this case. I have restarted router as well, but it doesnt help. Router settings conform to the suggestions above (and they worked fine for last 2 years, and it was not re-configured).

Please describe what error 3900 exactly means and how does it happen that old password remains after the complete systme restore?

Also why the system doesnt suggest to reenter the password?

Both devices 3rd gen

Can I expect an answer, please?

I'm desperately necro'ing this thread because it is happening to me and I can't seem to figure it out. No information exists on error message -3900, and it just continually skips the password portion, just goes directly to the error message. Need some help. I've done all the resets (can't restore since I can't connect physically), for both Apple TV, modem, router, etc... Still nothing. Everything else I have is connected to this network and I haven't had a problem.

Please check that your router does not have Access Control enabled. If you are using it, you need to have it accept the ATV MAC address. In my Netgear router, when ATV tried to connect, it appeared as "blocked" in the router setup and I could "allow" it. Remember that ATV has two MAC addresses, one for WiFi and another for ethernet.

Also, please review these recommendations Recommended settings for Wi-Fi routers and access points - Apple Support

if tried on different networks (and different router too?) if still incorrect, then its either Apple TV device, original router (check for firmware upgrade, or buy your own and test)

I would bet money its router...