I know you said no hydraulic lines were removed, but, to me, the system sure sounds airbound.

Here's and abbreviated procedure, as to how I confirm (or not) in minutes: Plug both master cyl outlet ports. Pedal should be rock hard (or close, with power booster). Not? Bleed master. (Can remain mounted, just slam on some c-shaped tubes).

OK now? Reconnect front fitting (to rear brakes). Still firm? Great. Not, trouble's out back, bleed, excess shoe travel, etc.)

Repeat with rear tube (for front brakes) connected.

The whole process can be done in a few minutes, and, if nothing else, localizes the problem area.

Rick