Performance indicator help

Gidday people, I have a 69 Barracuda & it currently has a blank in the dash, so I have bought a Performance Indicator to fill it. After I had it delivered from USA to Australia I checked it by sucking on the hose connector & the gauge didn't move. I then tried it on the intake manifold (car running of course) & it still didn't work. I have taken the hose connector off and there looks like a screw head that blocks any pathway into the gauge - Is this supposed to be there? The seller told me it was working when it was removed & has returned my payment but I'm trying to see if I can get it working - any assistance would be a help.