Brand New Dishwasher Not Draining

About 95% of the time when I’m called out to fix a brand new dishwasher that is not draining, the problem ends up being related to the install.

I occasionally see crushed or kinked drain hoses but most often it is due to the knockout not being removed from the drain stub in the plumbing under the sink. Or, if hooked up through a garbage disposal = same thing. The knockout still in place.

This is a knockout that I removed from a garbage disposal yesterday. Not covered by warranty either so the dishwasher install just got a lot more expensive.