Failed to start PushBack With ATC Pro/X (P3D + PMDG 777)

[Eran]

Hello,

I've initiated a push back from the GSX inflight menu, The pushback vehicle appears and the statment "Captain,...Ready for Push Back" appears,
However , no actual pushback occurs.

I have ATC Pro/X installed + PMDG 777
All other services behaves as expected.

Any Ideas ?
Thanks,
Eran