Hi, guys. Better late than never. I had this exact same problem. I tried every solution posted here to no avail. I’m not sure if it’ll work for you, but here goes.
For some reason-Amazon being the cheapskates that they are-the Kindle paperwhite reader (mine is a 10 gen) does not recognize networks tranmitting in the 5 Ghz band. Most modems have 2.4 and 5 Ghz bands for WiFi. ‘MyModem 2.4 & MyModem 5.0’.
Choose the 2.4, and that’s it.
I hope this helps.