Dispenser Too Full
If you've accidentally poured too much dish detergent powder into the dispenser, the unit might be too full to latch. Use a small spoon to remove some of the powder and try latching your dispenser again. While you might be able to force the dispenser closed without removing detergent, this simply pushes the extra powder into the dispenser mechanism. This can cause problems later.
Dispenser Clogged
Regularly using too much detergent risks clogging the dispenser mechanism. When powder gets stuck in the mechanism that latches the door, you won't be able to close the unit. Try pouring hot water into the dispenser cup to dissolve powder residue. If you can't clean the powder from the unit, call a repair person who specializes in Bosch products to remove the detergent cup and clean it for you.
Broken Dispenser
Over time, detergent dispensers can break. If you are using the correct amount of dish soap and still cannot latch the unit, a faulty spring inside the dispenser might be at fault. Contact Bosch directly at 1-800-944-2904 to obtain the name of repair shops in your area that service the units. If your dishwasher is still under warranty, check with Bosch about getting the work done under the warranty.
Tips
If you use detergent tablets or packets instead of powdered detergent, you might need to crush the tablet into smaller pieces so it fits inside your dispenser, or adjust its placement. Do so in order to latch the dispenser. If your Bosch dishwasher has electronic controls, an electrical problem may be blocking the dispenser from closing. Make a service appointment to troubleshoot the unit.