[Technically this is Chapter 40 discussion, but while we're waiting for that thread to be created...]
So, dinnertime, and we find out the enigmatic Marce is a bit of a seamstress. Lehm's evidently done his research and found that May tends to be more confident when wearing her jester outfit.
As for the ring not working, it may be that Lehm's disabled it, on the other hand, it may be that in her current predicament, Bern's no longer wearing hers.