high pressure soap

i am having problems in one bay with my high pressure soap. what should i look for? All the other bays are fine but I am not getting any soap in this particular bay.

Its a solenoid valve, or your button/dial on your metering box is out of commission.

You may have a check valve on the line supplying soap/wax to that pump which is stuck closed. If soap and wax are both high pressure and wax is also not working, it's that check valve.