To unstick a parking brake, you can try the following steps:

1. Disturb the brakes manually. Apply and release the brake a number of times. Shift into drive and reverse, and back between drive and reverse again to slightly move the vehicle back and forth.
2. Push down on the parking brake and press it down as far as you can without applying too much pressure. Press down and take the pressure off, repeating that until you have attempted it enough to know whether that is going to work or not.
3. Check the wheel the parking brake is fastened to, and use a hammer or mallet to tap it and try to break off any ice that might be holding it back. Moving the cable around a bit can also help to break up ice.
4. Check the owner’s manual to identify the parking brake cable. Investigate any binding of the cable. Remove, replace, and/or clean components thoroughly.

I hope this helps!.