I couldn't find that A-Dapter on CW, so let me check:
The Orange and the Red extension cords are plugged into 15A/120V outlets...
The RV's 30A/120V campground power cable runs off the bottom right of the picture...
Now my questions...
In front of the man's right foot, is that TWO adapters plugged together?
Are the outlets the Orange and Red cords plugged into, on SEPARATE 120V circuits?
When it quits on the 20A circuit, what kind of adapter(s) and extension cord(s) are being used?
Is anything but the RV on the 20A circuit?
Have your friend look at the "A/C" Breaker in the RV's load center. If it's 20A, the A/C should run on a 20A circuit with a good breaker and no other loads but the RV. IF it's a good adapter and connected to the RV's cable. Cheap adapters and light duty extension cords won't pass enough current for an A/C.
I find it hard to believe a gizmo exists that'll piggyback two 15A circuits into one 30A circuit, all at 120V.