Then it would be great if the error message would be more precise... for example "port already in use" or something like that...
We have this problem sometimes, too.
When minecraft is unable to connect - it doesn't even show details on all (dedicated) servers. Also local multiplayer games are not visible.
Workaround here is: close the game completely, start it again. Then it mostly works again.
Version: 1.16.201
Windows 10 20H1
I have this again on 1.17.30, but different ports are configured in server.properties. But log shows:
So seems it uses default port and the configured one?!?