My dishwasher isn't cleaning the top rack at all. The upper spray arms don't seem to be getting any water.

Usually, this means the spray arm holes are clogged with food debris, or your main filter screen at the bottom of the tub is blocked. First, remove the top spray arms and clear all the small holes with a toothpick or thin wire. Then, clean out the main filter assembly. If that doesn't restore water flow, you might have a failing circulation pump or a diverter valve issue, which typically requires a qualified appliance technician.