Tried bleeding brakes with the hand held Mightvac. Connected to bleeder screw and pumped up a vacuum. Opened bleeder screw and heard release but no brake fluid filled cups.

Tried with brake reservoir tight and loose. Bleeder screw and hoses OK. What is the problem? May have to revert to two man system!
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F-250 2000 4x2 SC SD Long Bed, 6-speed, American Racing 'Kong Wheels, Glasstite Camper Shell & Vintage Airstream gone...! Replaced with vintage Pop-up Sunlight Truck camper that fits in garage.