Cannot connect to my SMB server on MacOS
I would use WireShark to capture the SMB2 packets and see what's happening.


Install home-brew if needed - https://brew.sh
Install wireshark brew cask install wireshark
Get a capture to the IP address of the server going and then filter for SMB2 traffic. You can tip open any responses and see exactly what's happening.


This is much better than just trying another server or another client or trying to look at the Mac console in my experience. If this is overkill, you could open console.app from /Applications/Utilities and see if there are relevant messages / errors at the time when the error is posted to your screen.