I get the above message when I try to start PRTG Network Monitor using the regular icon (PRTG GUI Starter.exe). It also says "Error connecting with SSL". If I manually browse to URL it works ok. I don't see any errors in the web server log but the core server seems to think there is a conflict on port 80/443. I don't see anything else running on port 443 and the server is configured to use HTTPS, so I don't know why port 80 would matter. I am running version 220.127.116.116+
It was running fine for a long time so I don't know what happened. I upgraded not long ago but it continued to work ok until now.
Any ideas? I might try another upgrade to see if it resolves it.