2004 gmc envoy shift in part , instrument panel says its in drive and my car wont start

Your vehicle has a shift interlock feature. When you press on the brake pedal a solenoid pulls a locking pin out of the way so you can shift out of park. First, check the fuse for the shift interlock solenoid. If that's good, either the brake pedal switch or the solenoid is bad. In the meantime, pull out your owner's manual and read up on how to bypass the interlock. There's a manual way to do it to get you started until you can get it fixed.

You have a bad shift Piston or piston seal. Rebuild time.

I am assuming the shifter will not move out of Park (you don't mention it). The shift interlock is not working. Thing you can do is turn ignition key little, but just before ignition comes on, and try to move shifter to N. At this stage you can start the engine and shift to D. This is a temporary solution to allow you drive the vehicle to a repair facility. If you are successful, it is the interlock solenoid that needs to be checked out.

The valve body has failed inside the transmission. . It's possible the shift solenoids or the transmission control module are faulty as well.

Before any parts are replaced, it needs to be determined if the brake pedal switch is being actuated properly and functioning properly. After that, the interlock solenoid needs to be checked, as well as the linkage.

sounds like shift interlock solenoid is not energizing if you look under steering wheel on cover there should be a little square plug pop plug out look in hole there should be a little white plunger take finger and push back on plunger key should turn to off position allowing key to come out if this vehicle has floor shift possible bad switch on shifter or possible bad brake light switch

door lock actuator solenoid ( inside of door) needs to be replaced

all vehciles have what's called brake-shift interlock. It means you have to step on the brake pedal to get the car out of park.
A solenoid is de-energized to allow you to move the shift lever.
You may have a bad solenoid or a short circuit. Check first to make sure there aren't other items using the same fuse too.

center console shifter? if so, likely could be a misadj shift cable, you can pull loose top cover per instruction maneul tells you how to get out of park till you can get it adj, or repaired

Pull hard on the steering wheel to the left and the steering wheel lock mechanism should release. I mean pull hard to left because shift interlock is froze if you cannot get it this way you will need a pro to help! Good Luck Mate.