Was there a change made that I missed? My level 94 can't use the mirror. Clicking doesn't do anything. I have previously been in all TBM zones on this toon.
There is one quest where you have to use the mirror on multiple steps while in the instance. If you die/leave the zone, the mirror won't work as normal until/unless you drop the quest. I am guessing this might be what is happening to you at the moment.
I logged back on to see if this was the case, but I don't have any active quests from TBM. So I tried the mirror again, and it worked. It's odd because the first thing I tried earlier was logging out and back.