I too am experiencing this issue again. Looking at other reports it seems like it affects even the more recent builds of connect wise control and not just the older ScreenConnect. The problem definitely appears to be Mono.
I am also getting this issue. It also appears to be an issue with older builds leading me to believe the issue lies with mono itself.
However having TLS 1.3 disabled before accessing the portal is not a long term option, or an option for everyone for that matter.
Customer support service by UserEcho