When calling someone who was very recently online, but closed their computer, calls have the little initialization wheel going on for ever, long after the daemon gave up completing the handshake. That problem might be in the daemon, it needs to be investigated.
This project is unfortunately no longer maintained. If a new maintainer wants to step up and take care, the project is archived here: https://invent.kde.org/network/ring-kde You can just clone it in your private namespace on invent.kde.org and if you have started to work on it and fixed/implemented something get it reviewed and the project unarchived. Sorry for the inconveniences.