Remove your drain cover and look for any obstruction.
Rmove the drain hose from under the sink and check for obstruction.
If a disposal is in line, check for obstruction there.
I tell you what I do on this one, and it does work most of the times. I keep a 1/4 size plastic water line, about 8 feet long. What I do is take the drain hose off of the disposal or whereever it drains to, and then turn the dishwasher on the drain cycle, and then hold the drain hose in a bucket, and then send in the hose to rooter out the line. Most of the times the plastic water line hits the obstruction, and then the water will fly out in the bucket. I did one on Friday. Give it a try. Tom