In Monal the groupchats seem to be constantly offline. No messages arrive in Monal and Messages in Monal groupchats are not send. The Groupchat works with Conversations and Gajim.
Monal: 3.8
Server: trashserver.net
Groupchatserver: draugr.de

I'm not sure if it's a problem only for Version 3.8. But with Version 3.7 it was possible to send messages in the groupchats, which don't work anymore. 1:1 messages work without problem and normal contacts are correctly shown as offline/online. I can't provide logs. I hope somebody else can.