Dishwasher not draining?

Had a frigadiare dishwasher that wouldnt drain, after trying the baking soda and vinegar trick MULTIPLE times, it still would not budge whatsoever. uming that this dishwasher had a bad pump, and seeing how it came free with the house, I got my parents old dishwasher that worked great at their old house. In fact, this dishwasher had a brand new pump, and yet we still have the same problem, it won't drain. The garbage disposal works fine, and i've also emptied the drainage tube so I know that's not it either. What could possibly be the problem!!