[tomsem]

You might want to try turning off 2-factor authentication on your Amazon account before attempting it.

If you have it on, you have to supply the code Amazon sends to your phone/email (I cannot remember if you enter it as part of the password, or if a separate dialog is supposed to come up). With it turned off you would just supply the password as normal (and you can turn it back on after this experiment). At least this will help isolate the issue.

With the latest Paperwhite (maybe it works with any Bluetooth-enabled Kindle that can run the latest software?) you can register using the Kindle app for iOS/Android (maybe newer Fires). It has a way to share the WiFi and Amazon credentials with the Kindle (using Bluetooth). I did this with mine. But that is of no help in your situation.