I am sorry to hear that. I think that, given that your Kindle is quite old, you might perhaps have a Kindle that has failed somehow in its WiFi capability. (But, if you 'see' the WiFi that you are trying to connect to, then I think that it is not necessarily a failure.)
Have you tried removing the WiFi entry in your Kindle's Settings, Network Settings, Wireless Settings (more or less)? That can be done, usually, by holding down on that entry, until a menu appears with Remove or Delete on it.
Then close Network Settings, re-open them and/or Wireless Settings, and select your WiFi from the list that should appear there. And choose to Connect, then when prompted for the password, enter it very carefully, with attention to the difference between UPPER CASE and lower-case letters... please tell me how that goes.
I will advise you further as needed.