Hi Mark. Sorry for your problem. The EPS switch will flash PR when it tries to start the pump, then it should start reading the actual pressure in the system. I have never encountered one that would just keep flashing PR. It sounds like it is trying over and over to start the pump. I would double check the wiring. You might have an M1 or an M2 crossed with a ground wire.
You can also bypass the switch and run the wires direct to see if the pump starts. If all else fails you can go back to the old pressure switch until we get you another EPS switch. It could just be a bad switch but, what it is doing is rare, so I really think you may have a wire crossed. Either way we are glad to help. And if I send you another switch, I can run it on the test pit before I send it, to make sure you don't have the problem again.