Hello All,
To fix this issue please ensure your router's WPA settings are not above WPA2.
WPA stands for wifi protected access which helps to protect WIFI passwords from being cracked. Login to your router go to advanced settings then wireless then security. Here you will see a drop down for security. if its set to WPA-3 please change it to WPA2-PSK (Do not worry this is still a secure protocol). Apply the changes to your router.
Once the change is completed you will need to reauthenticate to the network using the password.
I believe kindles cannot support anything higher then WPA2
Please let me know if this works for you.