When I click on change character/avatar there is nothing? Or if i’m on the EU forums somehow I have 1 of my characters but I can’t see any of my other ones?
If you are talking about the WoW forums then that is a known bug with the modified Discourse software they use for WoW. Sometimes logging in and out of the char in game helps. Sometimes logging in and out of the forum account helps. Sometimes switching browsers helps. Sometimes nothing helps but time.
There are some changes they have requested to the WoW forum software from Discourse. Hopefully that bug gets fixed when/if those changes eventually get here.