I think i'm having a similar issue. Trying to check PSI in tube with Bravo Pressure gauge
Assumed the nice coloured collars were representative of valve colour (so used the green one with black seal) on my semi recessed zodiac valve. Didn't work!! Tried every combination with (and without) them. Anyone had any experience on this please as feel like a right idiot on something so basic (didn't fiddle with the screw inside the pressure gauge as assumed factor set is correct).