Apple TV - Password is incorrect

What is your model Apple TV box? Identify your Apple TV model - Apple Support

In addition to the troubleshooting steps from R4FTY’s link —

1. Try the ‘Other…’ option instead of selecting a listed discovered network. Especially if the password has been changed.
2. For Apple TV (4th generation or earlier), verify that the router or access point isn’t set to use WPA3, as only device models from ~2018 or later support that. Instead use ‘WPA2/WPA3 Transitional’.

I suspect the issue may be we recently upgraded our home internet to 5G Broadband

I was able to login to the Router and confirmed the WPA settings are WPA2-WPA3-personal

I suspect you are correct. Something in the current settings isn’t yet compatible. See below.

Then I try to do a Reset > Restore - I get the message - "The Apple TV couldn't be downloaded at this time. Try later"

‘Restore’ tries to download from the internet – which won’t work until the network connection is functional.

When I select Reset > Reset All Settings - it goes through the process but when I select the WiFi Network it doesn't let me enter the password - but defaults to the incorrect password and I get the message - “The WiFi password you entered is not correct. Try again (-100)

It shouldn’t remember old passwords after a reset, so I think it really is about router settings that influence the connection protocol.

• I would suggest to change the SSID network name on the router, to something new (not previously used with your devices). [One additional character would be enough. Or make it something witty, without revealing personal information (family names or address related names could make you an easy target).]
• If WPA2/WPA3 didn’t solve it, try going further down: WPA2 or WPA1/WPA2 (if available to choose). If that successfully connects, try bringing it back to WPA2/WPA3 (for better security).
• Ask your ISP or the router manufacturer about router settings that might block a 2013 device from connecting.

Hello I think this would help! If your Apple TV can't connect to Wi-Fi – Apple Support (UK)

As best I can tell my unit is 2nd Generation A1378

Okay. The A-number should be in the small print on the bottom of the device, and also in the menu at Settings﹥General﹥About﹥Model﹥.

I tried selecting other and entered the WiFi details but it keeps defaulting to the saved password and giving the message “The WiFi password you entered is not correct. Try again (-100).” It doesn’t give me the option to enter the password

Sorry to hear that. I hoped and expected that it would give the option.

Were you able to check the selected WPA version on your router or wireless access point?

If the issue persists, then try resetting the Apple TV to factory settings. That would erase all customization, including accounts, but also delete any remembered Wi-Fi passwords.