Check your water/fill level?
Most units fill to just under the heater.
Note that there are a few that fill to just over it.
Often but not always the unit will be noisier if it is a low fill because the pump is sucking in air.

Below is a way to check if this is your problem.
Set up your normal cycle.
Let the unit fill then add a couple quarts of hot water.
Just be careful to not overfill it.
Do this for each fill during the cycle.
If the dishes come out clean then you know it is a fill problem.

Note that the fill is just a timed event so the unit does not know when it has enough water.
The float (level) assembly is just a safety device to prevent a flood if the control board does not turn power off te the water valve.

The common cause of a low fill is a partially plugged screen filter in the water valve's intake side.
Remove the valve and check/clean the screen.
Do not permanently remove the screen as it is there to keep crud out of the valve which could cause a flood.

Check the hot water temperature going into the unit (ta the closest tap will do)
It should be a minimum of 120 degrees F.

If you notice that your cycles are longer then it could be a heater problem.
The water is not being heated up by the unit.