If it is helpful when I re connect to ground power GSX continues with the messages, but I can’t push back on ground power.
In order to allow pushback in the PMDG 737, GSX checks the following:
- Wheelchocks must be removed
- the PMDG GPU vehicle must be removed
- the PMDG Air Start Unit vehicle must be removed
- the APU must be On
- the Pitot covers must be removed
There's nothing in the GSX code that ever checks for Ground Power (unless you meant the GPU vehicle) so, I cannot possibly understand why GSX allows pushback only when the Ground power (not the vehicle) is enabled.
And, in any case, if ANY of these constraint is active, you are supposed to see the GSX message window indicating all the conditions that must be satisfied. Assuming you have the verbosity slider up, of course...