Reversed Polarity and Open Ground

Most likely suspects are a failed shore power cord or a loose connection in the RV's load center. If you are using an additional extension cord and are using adaptors, both of those pieces should be checked also.

Plug the rig directly into the 30 amp source, then use the small outlet tester to see what it shows.
Problem could be something simple like a bad GFCI receptacle.
Another common troublesome area is the twist lock connector attaching the shore power cord to the rig if it is equipped with one. The conductors pull out at the screw terminals.
If you have one and can use a multi-meter test at the 120 volt distribution panel in the rig for continuity between the trailer connector and the rig's service panel.

We have tested using the cheap $10 outlet tester, checking using our volt meters and by also moving everything from one power supply to another. Our house is a 200amp 120 single phase service with our garage on a 200 amp 120 three phase service, thus we have two drops where we can plug in our 30A 120v service.

The surge protector does not show a problem until we plug in our trailer to the system, then it shows the "polarity reversed, open ground". We have disconnect our solar system from our trailer, tried "turning" off the trailers' panel and have not been able to chase down the issue. If we plug in a piece of shop equipment to the surge protector that is single phase 30A the surge protector does not show an error message...thus we are stumped as to where our issue lies. Probably have a short in the main power supply from the shore connector to our panel which doesn't surprise us when husband scoped inside the wall of the trailer and found a screw from the outdoor shower had been run through the main power. The manufacturer stated they fixed it last year, but now we really wonder!

We must have scared the OP off as he/she has not responded with make and model!
There could be other issues that may have developed.

Ozlander wrote:
Makes me want to run out and buy a surge protector / not.

That would be unfortunate because if used correctly a surge protector / EMS can really save you a lot of future grief. However, as with any manufactured product an owner needs to understand how the device in question is designed to work, why it may not under some circumstances, and when it doesn't what to do about it ... clearly the OP hasn't done any of this, which is why I suggested their next course of action should be to contact the people who made the darned thing and ask people who should have the correct answers, not WAGs.

SoundGuy wrote:
Why are so many so hasty to declare the OP's surge protector as faulty?

Old-Biscuit wrote:
WHY>>>>>>>>

Because OP was plugged in for 3 days in an outlet (OP has used previously w/o any issues) before problems showed up.

Testing outlet showed NO issues.

Really?? I must have missed that because as far as I can tell the only thing the OP has told us about any testing that's been done is - "We have done some trouble shooting on that circuit and on other circuits." What does that mean? - "some testing" :h ... she did not say anything about checking the source supply with a polarity checker, nothing about checking for voltage differential between the source neutral and ground, nothing about disconnecting the trailer entirely and seeing what the surge protector itself is doing. Until they do they're fishing for answers without understanding the problem.

Seems simple.......surge protector is suspect.

It may be BUT you don't know that, none of us would know that until any potential problems with the source supply have been eliminated ... as far as I can tell that's not been done so there's no reason at this stage to declare the surge protector "suspect".

YES......contacting mfg. is logical step

Exactly. :R

SoundGuy wrote:
Why are so many so hasty to declare the OP's surge protector as faulty? As pointed out in that No Shock Zone article I linked to earlier any of these surge protection devices can be fooled if there's sufficient voltage differential between the source neutral and ground ... so who's to say definitively that this isn't happening in the the OP's case? Have they checked? Have they even bothered to check the source with a polarity checker that would instantly indicate any wiring errors? I'll bet not, and I'd also bet that any differential that may exist is varying, which would explain why the surge protector is sometimes fine with it, other times not.

As for the surge protector itself "failing", perhaps it has, meaning perhaps in the past it's been subjected to an excessive surge and has in fact done it's job by sacrificing itself, protecting the trailer's electrical system. The OP seems to be awfully concerned that "the $450 surge protector that has lasted 18 months" has failed where in reality it may have actually done exactly what it was designed to do. To the OP - rather than continue on with these online WAGs call the manufacturer with the details of the unit you have and ask someone who does understand how their device is supposed to work. Good grief! :S

I'm with SoundGuy on this one. I would buy or borrow an outlet tester they are less than $10 and come in handy from time to time.

Link
Or this one that can also be used to test GFCI's.
Link
Plug the tester into a 30/15 amp adapter and plug it into the garage outlet. Do the LED's on the tester say the wiring is reversed? If not then remove the protector and plug the trailer directly into the garage wall. Now go plug the tester into an outlet in the trailer and see what it says. If the tester says the outlet is good then the surge protector did it's job and now needs to be replaced. If the tester shows a problem then the surge protector is doing it's job and the problem needs to be fixed in the trailer.

After this the OP should use the adapter and tester to test the campground pedestals every time before he plugs in his trailer.

If the OP lived anywhere near me I would drive over with one of my many outlet testers and test his setup for him.

Another WAG: The OP has by now, wiggled the extension cord and found that the surge protector is working again. They gave the dog a severe look and made a mental note to pick up another extension cord that has an intact ground.

SoundGuy wrote:
Why are so many so hasty to declare the OP's surge protector as faulty?

WHY>>>>>>>>

Because OP was plugged in for 3 days in an outlet (OP has used previously w/o any issues) before problems showed up.

Testing outlet showed NO issues.

Seems simple.......surge protector is suspect.

YES......contacting mfg. is logical step

Makes me want to run out and buy a surge protector / not.