Hi! Marco. Thanks for the details. I'm here to help.
Try to enable SMB 1.0/CIFS File Sharing Support on the Windows 11 PC
Because older systems (Windows 7, 8.1, many shared printers) still rely on this older sharing protocol, Windows 11 can detect them but cannot connect unless SMB 1.0 is turned back on.
How to do it:
Press Win + R → type:
optionalfeatures.exe
Scroll down → Check SMB 1.0/CIFS File Sharing Support
You can select SMB 1.0/CIFS Client only if you like.
Click OK, then restart your PC.
After reboot, try accessing the other PCs or printers again with:
\\ComputerName
or
\192.168.x.x
See if this helps. If you need further assistance, just let me know.
Best regards,
Kimberly