Unmount your drive letters and mount them again.
Delete stored network credentials on the workstation, then try again (Credential Manager on windows 10/11).
If you have the same username on both machines, the password must also match.
To access without a user/pass, make sure Guest/Anonymous access is enabled on the server.
If the user account doesn't have a password you need to enable Allow Blank Password policy on both machines.
Make sure the same SMB level is enabled on both machines (SMB v1/v2/v3)
There are many other possibilities. Google for "windows network share permission" issues. I don't think MC does anything to cause that, it's likely something else that caused it (for instance, some windows updates may make breaking changes such as disabling SMBv1).