If your dishwasher won’t drain properly, you may have a problem that requires a professional inspection or a reasonably straightforward issue, such as a clogged air gap. The air gap is a device designed to prevent water in your sink from entering the dishwasher.
If you have one, it’s a small, round device right next to your faucet. It is easy for this to get clogged, especially if you don’t scrape larger food particles from the dishes into the trash before loading them into the dishwasher.
Here is a video that shows how to check it for blockage