Authentication problem means wrong password for the WiFi you are trying to connect to. It is possible the WiFi password got changed, or something else did. You say in the title 'any WiFi' but in the message mention only 'one WiFi'. Can't be both.
If you were connected to the WiFi you are referring to before, and now all of a sudden can't, then something was changed. Password, channel, etc. You would have to talk to the person who has control of the WiFi about it.
However, if you find they have changed nothing, then make your phone 'forget' the WiFi info, restart (turn off and back on) the phone and then try reconnecting to it. To make sure you get the password right, you may want to turn on the option to see it as you type it (rather than the standard * that are normally shown). And make sure to check if anything is case sensitive.