I am getting the same error in the PMDG 737-700. Keeps asking me to release the parking brake which is set and the red light is on for the brake. I didn’t release the brake again, And keep getting the same message please release parking brake. This is very frustrating. I went to the PMDG forum and checks for the issue with the brake and I am doing it the correct way but GSX is not Recognizing that the brake has been released.
Jeffg