Remove the front panel and also the hose going into the small electric pump you'll find right in front. If something is blocking the flow, it's likely there. Other than that, the outlet from the tub may be gunked up. In this case, fill the washer on the lowest level with very hot water, add a cup of powdered dishwasher detergent and let it circulate a few minutes, then set the timer to drain.
tip: Never use drain cleaner in a washer..it will ruin the seals.