Jitsi Android app: connection in progress

I’ve got Jitsi set up on my Ubuntu server fine. I’ve set up user accounts so that meetings can’t be created anonymously. Now I’m trying to connect in from Android. The meeting is currently empty. I get to the point where I’m prompted for the username and password, but before I can enter it, I get a message that the connection is refused as another call is in progress. There is no other call & I’ve also cleared the app’s data and cache.
Any ideas what I can try?
Thanks, Warren