yeah... remove the check valve. i'd return it to the hobby store owner and complain because i think he really didn't give you good advice.

then i'd check the tubes. i wouldn't be surprised if you had an air leak somewhere and that's why you're not getting any fuel.

if it still doesn't run, maybe remove the top wing, turn it over on a stand and start it up right side up. see if that works. a little unconventional but at least you know if maybe it's the engine that's not running right.

upside down engines generally flood. i'm surprised that yours is starving for fuel.