The change would have to be made at the park end (inside the park box) screwing around in there is both dangerous and likely to get you invited to leave.
You said you tried using your 30 amp adapter... I assume you were connecting to the parks' 30 amp outlet.
For this you need TWO adapters. One is 30 amp to 50 amp and the other is the other way around YOU MAY NEED TWO OF THE 30 to 50's (the one you do not have now)
Using an ohm meter find which side of the 50 amp plug connects to the hot slot on the 30 amp adapter You want two adapters one that connects to the RIGHT side one to the LEFT side.
Then you choose the one that works (you can pick which side) once you get 'em identified the same way they are on your surge guard Label them 1 and 2 and plug in as follows
The labeled adapter to the park
Your existing adapter to the labeled adapter
Surge guard to labeled existing adapter
CAUTION you can draw more than adapter designed for
Better option
Make a 50-50 adapter (or two)
These will need like 8/3 or 6/3 wire (Black/White/Green
On one go from the left side of a 50 amp plug (Black) to both sides of teh outlet (White goes from the center flat blade to the center flat slot and green is the round pair)
On the other from the other side on the plug to BOTH sides on teh outlet
again, Plug one in.. the display will either show the higher or lower voltage. if it is the higher lable it L-2 if it's the lower L-1
now when you pull into a park wiht issues, use the proper 50 50 adapter
This will NOT be overloaded but it will cut your total power in half.. Usually thyis will NOT be a problem but you may find occsaion where you need to shut the water heater off.