Possible No flow to heater core?

Hi, I hope everyone is doing well. I’ve been taking some time to work on my 225 74’ dart this last weekend, and I’ve encountered something that’s baffled me. My heater currently does not work, and I decided I likely needed a new heater core, but I also decided I would continue with a coolant flush and fill. I wanted to flush the heater core aswell to see if it was getting flow or not, and I also checked the vacuum control valve on the inlet hose. Both seemed to flow well and the valve functioned well. I then proceeded to flush all my coolant, clean with a system cleaner and refill and bleed air. Out of curiosity I checked to see if my heater would now work with a cleaned system, and of course it still did not blow anything but temperate air. I then got out to feel the heater core inlet hose after the car had been running for about 20 minutes, and sure enough it wasn’t warm at all. I’ve looked around but I can’t find any help or answers on why my inlet hose isn’t even receiving coolant at all. I’ve also done a thermostat and gasket replacement so I know it’s not that. Anyone have any ideas? Is vapor lock in the heater core a possibility? Thanks.