EDIT II:
Now after retrying, the page doesnt show "service temporarily unavailible" anymore, now it says that my verification level isnt enough. Although Im verified on tier 3, and for the amount I want to withdraw I would only need tier 2 anyways. Dont know what to do here.

Same situation here - tier 3 verified account and it says that current funding tier level (3) is insufficient for this functionality. I can't
withdraw anything!
Good to read that Im not the only one in this situation. Did it at first also showed up as "service unavailible" for you? I hope that we will get an answer from the team here!
Actually this is the first time that I wanted to withdraw something from an exchange. Hope that I wont be disappointed in the end.