It's the beginning of the end I tell you. What with this and the Marketplace being unavailable, it's the slow death of EQ Muhahaha!
The team is currently looking into this. If you're still having an issue with this, please let us know what server you are on when you reply here.
We tried getting the 1st Katta raid: Defense of the City, Argin-Hiz raid: Burn Out, Plane of War raid and WK 1 raid: The Doomscale Horde. All 4 instances refused to let anyone inside when using the proper keyword(typed or clicked). I am on the Erollisi Marr server.
Instances should be working again on Erollisi Marr. Please let us know if you encounter this on any other worlds.