Is Detergent remaining in the Dispenser?
Clean dispenser when caked detergent is present. Older detergent exposed to air will clump and not dissolve well, which will cause the dispenser door to stick to the detergent. Replace detergent if necessary and store the detergent in a tightly closed container in a cool dry place.
CLICK HERE for more information on detergent usage guidelines.
Was the previous cycle interrupted or were items loaded in the dishwasher blocking the dispenser from opening?
If the previous cycle did not complete, the detergent can become caked in the dispenser cup if it is left sitting in the dishwasher. Items blocking the detergent dispenser will keep it from opening. Make sure water action can reach the dispenser. Do not load large items in front of the dispenser.
Is the water temperature too low?
For best results, the water should be 120oF as it enters the dishwasher. Proper water temperature helps the dishes dry effectively.