Okay, not so clear on the title.

Say I last played on a Vanilla server. I launch DayZ and press Play. This refuses my connection, as the game is trying to connect on a character which is on a modded server for some reason.

I go to server browser, click the server I want to play and join it. Nothing happens. The game does not let me join this server. Press join as many times as you like, it won't do anything./

Only solution is to restart the game and make sure you join the vanilla server and not the modded one by accident again