Do you have a different pedal set than the usual Thrustmaster ?
If you have a different one ( a Fanatec for example ) I might have a solution as mine ( TS-XW now but same for T300RS before ) is often perfectly detected but regularly looses its FFB at the start or even at a session change ...
What makes it work in this case ? .... strangely just the change from "Combined" to "Separate" or the same but inverted for pedals in the Thrustmaster Config Panel . .....
Strange, I know ... as I don't use their pedals but it works every time I need it.
But GTR2 needs to be closed and restarted.