IF you tested the First switch, IT may be dead..(the reason you were drawn to the repair..) Toss that one in the trash.
Take ANY of the new switches, and your test lamp, or meter, go to the gas station, hook either the test lamp ACROSS the terminals (if the lamp has it's own battery's) OR your Meter set for continuity / Beep..
Insert the air nozzle into the switch orifice and give it a blast..The lamp should light, Or the the meter register/beep..IF not the switch (s) is / are Defective..(and a bad batch from the same store would not surprise me).
If it does light, you need to inspect the differential valve or proportioning valve on the line from the master cylinder..
Also remember: Front pressure will Be slightly LOWER than rear pressure..which may be the problem..