@BF-Frederic If it worked in 5.3is it possible you used up all your encoder sessions (e.g., running too many VCams or having OBS or some other encoding software running)?
Normally, when that happens, it means people are using a GPU that supported H.264 encoding or are streaming to a device or browser that didn’t support H.264. But if it works in 5.3 then that does not sound like the case.