No oil pressure

This car lost oil pressure while driving. I put a gauge on it at the oil pressure switch and had 0 oil pressure. I pulled the oil filter and verified tha there was no oil at all being pumped. I replaced the oil pump assembly and now have oil voulme but still no pressure. I removed the front cover to verify I had the passthru seal correctly installed and making contact with the oilpump output. I removed the oil filter stand and checked for blockage then pressurized the oil galley from the front cover to the oil filter stand and the oil pump assembly there is very low leakdown. Is there an oil pressure regulated located after the oil filter? Or what else could cause this problem?