Impossible to get AT port in Win11 for EM7455

[jyijyi]

could it be working in another USB port?

Do you have VMWare Ubuntu image?
You can route the USB to it and see if it can communicate with AT commands

Lastly, there could be a chance that there is whitelist modem list in your PC:

Sierra EM7355 Not working on Lenovo P50

I assume you’re getting that message printed by the BIOS itself, so there is no point in attempting to install any Windows drivers from anywhere, as the system is not even booting. The problem seems to be that the EM7355 isn’t listed in the Lenovo P50 whitelist of WWAN modules. See, manufacturers don’t want you to install any kind of WWAN module in the laptops, they have a device whitelist that says which WWAN modules you can install, and the whitelist is hardcoded in the BIOS so you cannot c…