As noted by a few above, the key is to "burp" the PV before pumping. The seals in the valve are pressed into the seats by the high pressure inside, and after a few hours that way get stuck.
To lose the minimum air possible, I use the pump chuck and hose and bang it against the valve (after backing off the nut). The small Psst is testimony that the "burping" successful, then I attach and pump.
In 9 out of 10 cases the only issue is in the valve itself, and has nothing to do with the pump.
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FB
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