Pico 4 NOT detected by FS VR

Do you have the same issue if you follow the OP’s steps to reproduce it?

?

Provide extra information to complete the original description of the issue:

In FS, Click on start VR. NO VR HEADSET DETECTED.

If relevant, provide additional screenshots/video:

Using Pico 4 headset, connection is USB Cable. Start Virtual Desktop, start FS and then Options, select VR mode and a warning comes up. ‘No VR Headset Detected’ ?
I have Steam VR active. The only thing I can think, is that FS has to be the Steam version, and FS started from inside Steam VR. Which means that if you have the Microsoft Store version of FS, the Pico 4 is not going to be recognised? Surely, this cant be? As far as I know, there is no way I can add a non Steam purchased game to the Steam library?