Ok, you 50 amp folks ... He alrady stated it is a 30 amp model.. Original post.
And yes, they do not work with open neutral.. Even if the safety ground is good.
The surge guard may object to open ground as well (not sure have to re-read manual) but the RV will work just fine if you bypass... So long as it does not kill you.
I have a 15 amp to 30 amp "Puck" type adapter (The word PUCK describes it's appearance) and a 3 light outlet tester.. Works well for testing 30 amp holes in the box to check for open ground/neutral and inverse polarity.