Jami rejects outgoing calls immediately

I have Jami installed but I rarely use it. I decided to try today, when I call a contact, the call is immediately failed. I am on GNU/Linux, Debian, using the last version from Jami repository.

I tried with the F-Droid version from Android, same result.

My friend called me from his iPhone, Jami on the computer rang and I could answer and the call was working. After that, I can call him for a little while, then it does not work anymore, I have the failed call immediately again.

For these tries, we are both connected to the same local network (phone with wifi, computer ethernet, DHCP address allocated by the same server).

You have to wait ~30 seconds (or even longer) before you make a call.