After having a new dishwasher installed, there has been a persistent mildew smell coming out of the drain nearest the dishwasher.
I have used vinegar and baking soda to move any junk. A week later I tried bleach down the drain.
What do you think the problem is?

Do you have an air gap on the sink for the dishwasher? Does the dishwasher drain into that side of the sink?

Yes to both questions.