I have a GE Twenty Eight Hundred dishwasher (Model# GSD2800D03); the detergent dispenser is stuck in the closed position, and the machine throws a C8 code on the digital display, during its cycle, around 5-6 mins into the cycle. Reset button clears the code, and allows a new cycle to start, but each new cycle results in the C8 code and the dispenser cup still has not popped open. Water is filling and draining fine, and everything except the detergent dispenser seems to be working fine. This model has a dispenser cup lid that requires the user to manually twist the cup lid closed after adding detergent. How do I get the dispenser cup lid to release, and operate properly during the wash cycle?

most likely issue is that there is clumped detergent in there that has glued the mechanism shut. try to muscle the thing open... not like a wrestler, but pull about three times as hard as when you twist it shut. if that doesn't work, depends on what declumps your detergent... I'd start with vinegar.

the other possibiilty is that it's clumped shut, and the solenoid that tries to open it when the timer tells it to has broken, or has broken the level on the back side of the dispenser. fixing that probably requires taking the liner out of the door, new gaskets, etc. and may well be best done by a service call.

Thanks for your reply...

Unfortunately, it's not clumped soap. I have disassembled the thing now (and verified that the cup is clean as a whistle), and reassembled, yet the problem persists.

Thanks! I actually found another site offering no-cost/low-cost suggestions for troubleshooting the issue. Turns out it was a small piece of foam insulation (there only for noise reduction) inside the door, near the cup lid arm that was preventing full release of the arm during the wash cycle. I removed the foam and ran the dishwasher twice; everything is working fine (for now!). Thanks again for the replies!