Verify your setup...first on the GPxPatch and then in the game.
Could be that you have No engine sound selected in the GPxPatch.
Good luck
GPGSL-3: VTR Driver, S4~S11 (2nd,
1st, 2nd, 2nd, 3th, 4th, 3th, 2nd)(Constructorstitel S7 & S9)
GPGSL-4: ONE Racing Driver, S8~S11 // TYRANT Racing Driver, S12:
1st, S13:13th, S14:
1st, S15:13th //
WREXHAM Motorsports Racing Driver S16: ?