The only reason for an authentication problem is the wrong password for the wrong WiFi. So not only be sure you are inputting the right password, but that it is the right WiFi you are trying to use it with.
Also, try using other WiFi and see if you have trouble with them. if not, then it is definitely the one you are trying to use and getting the error with. If it is your own WiFi, then check the modem/router settings to make sure the WiFi password wasn't changed. Also check the settings to make sure the device wasn't blocked. It happens.
If it isn't your WiFi, then you need to check with the owner.