Board Thread:General Discussion/@comment-31832165-20170517234623/@comment-30549602-20170518061715

What VesperTx said. If you get the message saying you cannot create an anomaly right now, it means every room must already be cursed or in CBA mode. Unless a room is at Novice level. These do not take curses.

So maybe the room is cursed, but with wrong one? Play with or dispel the wrong curse. Play one more game to take it out of CBA mode and then launch the correct summoner. Dispel. Item is rewarded. The wiki has great info on summoning, btw.