if the standard methods (pressure release valve screw behind passenger seat, and cable release for backlid latches) do not work, then unbolt the two pins with the two pairs of 10mm bolts and manually lift the deck, release the front with the allen wrench and manually finish folding it into the roof storage compartment. In my case the cable tensioner motor gear had stripped, which is a common failure with this (German) roof system from 'Capote'.
Also remove the panel behind the seats so you can see the drive motor behind the driver's seat.
Without taking the rollbar covers / speaker grills and top cover off, you can verify and check the tension on the two cables. If when closed these are all the way to the right (facing towards the rear), with the cable ends bend (these are 2" straight end pieces), a simple fix is to adjust the small 9mm nuts (use a small vicegrip with tape to protect the threads) while holding the threaded ends, and adjust clockwise, by a couple of turns at a time. The system will reset when the ignition is turned all the way off (key-out) and then back on. Replace the rear deck pins - watch the shims (use some scotch tape temporarily if needed).
If it's still dead, use the override buttons in the rear glove box. The front button works the pin latches on the front window frame, the rear button operates both the pin-motors in the rear deck and the latch motor, of which you just adjusted the cables (if you went down this path).
