I worked it out.
I saw my screen and it had flight sim in it. Ctrl tabbed but it would still show the virtual screen but with two screens instead of one. So.
What i had to do was load VD , Load MSFS, Quit Steam VR in VD. (had to close the .exe in task manager to because I don’t know why). Then CTRL tab into VR with MSFS. Then VD would have the switch to VR mode then it would work. For some reason i can’t switch to VR in VD without Exiting and restarting the steam VR client.