How do I gain access to a wiki?

i have a pbwiki account, and i am logged in, yet when i try to post a comment, or edit the wiki for a class i am taking it says i don't have permission. and when i click on my teacher or my classmates user it says that i am not logged in when i am. I also cannot add the wiki to my list. I've been trying to get on to it for weeks and nothing seems to work!!!!