Often this is due to someone filling the rinse aid dispenser with dish soap.

If this is the case there will be lots and lots of suds.
It will take a long time to clean out the unit.
It is best to just replace the dispenser.
Then run the unit adding a cup orso of vinegar to each fill until the suds are gone.

I am not sure that the above is your problem.
There should be very little suds with dishwasher detergent.
So if the suds are more than they should be but not overly excessive try a different detergent,
The powder type is still the best.