My dishwasher is not draining. It goes through the cycles but at the end of the wash, all the dirty water is still sitting in the bottom of the dishwasher.

Could this just be a blockage or something more?

Yes, could be blockage in drain hose. Do you have garbage disposal? Do you have air gap vent on sink?

Do you have a high loop or a counter top air gap installed? Let me know. Tom

Disconnect the drain hose at the sink trap connections and try to blow air back up the line. While this could be a bad solenoid on the drain gate it is frequently just debris. After blowing air up the line direct the hose into a 5 gallon bucket and try running a short cycle. Inspect what comes out, if any debris then repeat the blow and short cycle over and over until clear.