What USB -RS485 converter are you using?
I don’t think the baudrate is the issue; more likely that the USB/RS485 converter is no longer recognised as such; or something like that.
See also here: Lost connection to smart meters after upgrade to venus 3.55.
The log files to check once logged in are /data/logs/dbus-cgwacs and perhaps some related to serial starter.
Info on how to check logs is here: commandline operational · victronenergy/venus Wiki · GitHub