I’ve recently moved into a property with the above built-in dishwasher.
It has, after a few washes, stopped opening the detergent drawer to release the tablet. It also seems to wash for hours before finishing…
It’s a Whirlpool in a dress. Certain “no heat” conditions can cause the dishwasher to run for hours. If the dispenser won’t open it’s almost certainly the release solenoid which has failed, so a replacement dispenser would be required.