I have the same problem with no pressure. Have an above ground pool with a Hayward pump and DE filter. We took the filter apart and cleaned it, the pressure was great for a few days, now nothing again. Took each hose connection apart and the water flows through with no problem, but there is no pressure when everything is connected again. ~Ellen
Are you adding DE into the filter after you clean it out?
After washing the entire filter are the fingers inside of the filter nice and white?
Is this a Hayward Power Flo Pump Or Super Pump?
Those are some common problems that many people experience.
Make sure you pump impeller is not clogged and the eye is free of debris.
Sometimes the impellers on the pump get clogged and then the pump will not ave enough pressure to pump through the filter.
I would check the above and let me know if you need more help or ask more questions.