Platen stuck in base - chances are the clamp is out of alignment. Ask customer to check the alignment down the hole. If not aligned then hold clamp with pilers and turn so the claw is as in the picture below.
If platen is stuck in the base then 2 person job to try and remove. One person to try to pull the platen off (keeping it straight) whilst the other person marginally turns the clamp to line up and release the pin. This may take a bit of time and patience.