Quickest test is the one I gave you. Place meter leads across the switch and should read 24vac IF it has power to it.
Then after 30 seconds or less/more, IF/when it closes, you will suddenly read 0vac.
IF it does not close, you will continue to read 24vac.
Yes, I believe the switch is not working. Check the tubes connected to it for loose, cracked, kinked or clogged.
If ok, be sure booster motor is running strong and smooth.
Also check air pipe to booster motor for blockage or separation.
IF air pipe, booster motor and pressure switch tubes/hoses all seem ok, then switch is probably bad.
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?