Assuming you meant this happened after a pushback, I just tried a pushback now with the PMDG 737-800, and I cannot replicate what you are reporting, see the video here:
https://www.youtube.com/watch?v=VWU7dZceVXQDon't mind a few issues I had with the parking brake, it's only because I don't have actual rudders, so the special custom handling of parking brakes with the PMDG doesn't play that well with my joystick assignment ( or maybe I still haven't fully figured it out how it's supposed to work... ), but it's nothing related to the issue you reported, which seems to be the engines stuck for some reason.
As you can see, there are no problems with the throttle and to increase N1 to taxi away normally after pushback ended. If something like this really happened to everybody, and for weeks, we would have the forum flooded by similar complaints, but there are no such reports.
Of course I deleted GSX pro then I reinstalled it, but no improvement. I can't understand, before that everything was working perfectly.
Since the problem doesn't normally happen, it's normal it won't be fixed by reinstalling GSX. It must be something else, possibly a 3rd add-on that causes this conflict which for some reason happens only together with GSX, which might be easily mislead you to be caused by GSX, when it's not.
Note that, I'm using SU12 Beta, with the upcoming GSX update that will support its new features so, it is possible some kind of problem in the previous sim updates might have been fixed with SU12 so, I suggest waiting next Tuesday for both the update to the sim, and the GSX update as well, which will come out as soon the sim update gets released by Microsoft.