As Florian mentioned, there is restriction on sending messages with previous event id. you can send it without previous event Id.
Do you have the same problem when using the other client like https://groups.nip29.com ?
I'm looking for help with this issue https://github.com/max21dev/groups-relay/issues/4
I'm using groups-relay which is built on top of khatru to host the noStrudel, blossom, and nsite groups. but there is an issue with chachi / flotilla and the relay which is making it so when users send messages the relay rejects them and no one else in the group see them
I'm not sure whats going on and I don't have the ability to debug it without taking a week or two to learn go
Discussion
Looks like it works from https://groups.nip29.com but I'm guessing that's because its not adding any previous message ids
The odd thing about the issue I'm having with chachi and flotilla is that the previous ids that are sent come directly from the relay as the latest messages