Does anyone have any insight on how to adjust the pressure switch on my Coast spa? Thanks

I don't recommend adjusting pressure switches. They are a safety device for the heater. I recommend replacing it.

I am curious about the same thing. Peteyboy is probably right. You don't want to adjust your pressure switch and then wind up melting your wires, or worse because the heater was allowed to run without enough cool water flowing though it.
It seems there may be times that an adjustment is required, and there is a flathead screw, or thumb knurl know, or some way to adjust most of the older pressure switches. Unfortunately, I do not know which way to turn the screw, or how much to turn it. Before messing with something so very critical as this, I would first run the tub without any filters just to be sure it is not simply a clean looking, yet clogged filter. I would also remove the pump and actually look into the intake for partial clog, or hair, or anything that could affect flow. I would also buy a new flow switch ( only 40 bucks) just to be sure.
After being absolutely sure that the flow is as good as it can be, I would slowly turn the dial 1/8 turn at a time until it turns on and the heat goes on. I would then have to monitor the heater and watch it for several days to be sure I have not solved one problem and created a hazard.
There are places to buy a pressure tester. If I get one more customer who has a boarderline flow problem, I will buy the tool, consult with the manufacturers tech support people and set the switch to the exact pressure point recommended.
Perhaps the spa doctor can educate us further on this subject so that we can truly and completely understand.