DMs have been iffy for a while, I think due to relay selections. They should be much better now, and generally work for me, but I haven't tested them thoroughly. Are you unable to receive or send? When you send, do the relays you use give you any OK=false messages or notices? 

 Last I tested I was able to receive but not send (just using NIP-65, so relay selection is the same across my several clients). 
Next time I'm able to login(trying daily) I'll test and let you know.