Dishwashers are fairly reliable as far as household appliances go, so we tend to overreact when something goes wrong. Many people immediately call a repair service when their dishwasher's latch malfunctions, and while this may be necessary, there is also a good chance you can repair the latch quickly and easily on your own. When dealing with a malfunctioning dishwasher, remain calm and evaluate the situation. Also make sure that while repairing the dishwasher you don't create a tripping hazard with your tools or other supplies.
Make sure that the dishwasher is not set to its wash cycle, as this setting will cause many models to lock the latching mechanism down. Change the setting to "Off" or "Standby," and check if you are able to use the latch again.
Examine the latch mechanism from the outside of the dishwasher door, looking for anything lodged in its track that may be preventing the latch from being fully moved into position. Use a flathead screwdriver, knife or anything else that's small enough to fit inside the latch to remove any blockages.
Check that the countertop and surrounding cabinets are not in some way preventing the dishwasher door from closing completely, which could prevent the door from latching properly. Also check all of the dishwasher door seals for any obstructions that might prevent the door from completely closing.
Examine the inner side of the latching mechanism on the dishwasher door. Look for any blockages wedged in front of the pivot point, and also make sure that moving the latch handle on the outside moves the actual latch mechanism. If the actual latch is broken, it will need to be replaced by the manufacturer.
Examine the hole into which the latch is normally inserted. Remove any lodged debris and look for any broken pieces, specifically the post the latch connects to. If the latch post has broken, the entire inner housing may need to be replaced, or just the post itself. Contact the manufacturer for replacement parts.
Examine the door hinges. Remove any blockage that might keep the dishwasher door from fully closing, which in turn would prevent the latch from working properly.
Ask yourself if anything out of the ordinary has been done to the dishwasher, or if it has malfunctioned in any other ways. Often, the answer to this question will lead you to the solution to any repair job.
Check your dishwasher's warranty before attempting any home repair to ensure that nothing is done that could void your warranty. While it can be tempting to just get something fixed as quickly as possible, it is never worth risking your warranty.