Not all MSX games actually work over a null-modem cable. Here's the for link play:
The updated fix focuses on enhancing the stability and compatibility of multiplayer connections on MSXBL. Key improvements include: msxblmultiplayer link fix updated
Right-click the button and select Terminal (Admin) or PowerShell (Admin) . Not all MSX games actually work over a null-modem cable
Select and click Start troubleshooting . msxblmultiplayer link fix updated
By following these steps, you should restore the connection between your browser/launcher and the Xbox ecosystem, getting you back into your multiplayer session without the "msxblmultiplayer" headache.