Hard Pedal w/just installed Power Assist

Dart 67, had manual drums. I bought a used booster/master assy from someone here.
Everything hooked up okay, I DID replace the master with a rebuild as it had a bit too much "junk" in the rear reservoir. We bled the brakes and no vacuum leaks.
Still it's a hard pedal.
1.Anything to do with that "filter" assembly/gasket(?) between the master and booster?
2. Could the booster itself be bad even though there's no vacuum leak?
If so, who rebuilds these things OR is there a consumer rebuild kit available?
3. Something I could have missed?

Appreciate any thoughts here guys.