Fresh install rejoining meeting

Dear all ,
We did a fresh install on ubuntu 16.0.4 of jitsi with a self signed certificate
it constantly rejoins the meeting even with one participant ( definattely fails when a second one joins)
no errors in prosody.err and no error in general ( check and browser console both chrome and firefox)
any ideas ??

Check jicofo logs and jvb logs.

Well i guess i found the root cause cant find where to change it.
It works fine using ip address fails when using dns name.Dns resolv correctly both on jitsi host and all network pcs .
Reinstalled using ip adress everything ok.
Reinstalled using dns…fails on second participant join…
The install in both cases is fresh na both cases use self signed cert. And no errors in any of the logs…
Any ideas ??