From the original post it sounds like you have few options to help figure this out.
The issue is your house 30 amp outlet only feeds one hot wire. A 50 amp outlet has 2 hot wires. You are using an adapter to split from one hot wire to two hot wires.
If your RV has a 50 amp cord then it has two separate hot wires coming in. In simplified terms; One wire provides power to run the AC's. The other wire provides power to run the refrigerator and other stuff.
Your 30 to 50 amp adapter is supposed to take the power from the one hot wire from the house and split it into two hot wires going to the RV. You need to figure out where the second hot wire is broken (not getting into the RV).
In the RV check the breaker panel for a tripped breaker.
If you do not have a multimeter try borrowing a different 30 to 50 amp adapter and test.
If you have a multimeter then set it to volts AC and check at the house wall plug and then at the end of the 30 to 50 amp adapter. you are looking for 120 volts in all checks like below.