Authentication error means one of the following is happening...
1. You are inputting the wrong password to the right WiFi connection.
2. You are inputting the right password to the wrong WiFi connection.
3. You are inputting the wrong password on the wrong WiFi connection.
In addition to the above, if you have a modem/router that allows for both 2.4GHz and 5.0GHz, the passwords and names for the WiFi connection may well not be the same for each one.