It's not going to be DE. There is no setting where DE transits the pump unless something is seriously misconnected. How much did you dismantle to do the cleaning?
If you have an MPV set it to Waste. This will tell you if problem is in filter/returns (if you get good flow to Waste) or pump/suction lines/MPV (no flow to Waste).
I may be a noob here but I have been at this a long time.
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