Pandaria Worgen Two forms isnt working

[Ggold]

hey, from level 1-89 it didn't work (cant transform back to human) but since i saw a level 90 druid "human" i knew that it was possible at level 90 (or so i thought)
when i reached level 90 it either did nothing when i clicked it or gave out the message "cannot transform right now"

if any1 can help or has a solution i would really appreciate it

edit: server is frostwolf