No drain BSH dishwashers:
1) Is the filter screen at the bottom clean? One BSH trainer told me he cleans his once a week. I know exactly none of my customers are cleaning theirs that often. One of the most common slow drain/no drain problems is hard water/detergent build up on the screens.
2) If the filters at the bottom are clean and passing water easily, then take those out. Is the little cover still over the drain pump? If it's not the drain pump just cavitates the water. If it is still there, get a torx screw driver and an 11" cable tie. Take the cover off, and plunge the cable tie behind the drain pump (towards the rear wall of the unit.) Fun stuff should bubble up.
3) While you're on your knees open the cabinet and make sure the dishwasher's drain hose is, at some point, higher than the point it drains to.
These three things fix the vast majority of my no drain BSH dishwasher problems. If all these are taken care of then we can start looking at more exotic ideas.
Source: Thermador DW won't drain DWHD630GCM/60