anything can stop the flow… like a plugged up fuel pick-up in the tank, plugged up filter in the side bowl. check tosee if fuel reaches it… if not backtrack (just remove it as a test or clean-it and blow it dry)
the carb inlet needle may be plugged etc… when was the engine used last ….last week 5 years ago ?? when was the carb serviced ??
The tank primer button pumps gas directly, it does not put pressure in the tank. The tank can have pressure from normal vapor pressure of the gas, which increases if the tank is in the sun, and that’s OK, and normal. Check the stuff Crosbyman mentioned.
Dave