This is what a typical PEDESTAL looks like wiring wise...
In your case it sounds like the GREEN WIRING shown is not connected.

You can TEST this circuit using a 120VAC VOLTMETER
50AMP SERVICE READINGS

30/20/15AMP SERVICE READINGS

You can also TEST the pedestal side using one of the circuit testers. You may have to use a proper adapter to adapt down to the 120VAC 15AMP connection.

You also mentioned plugging into the 50AMP side which tells me you may have a 50AMP Trailer. I am wondering if that is the case perhaps your 50AMP(F) to 30AMP(M) Adapter may be at fault. You must use a proper adapter being the RV long "DOGBONE" type adapters and not the small round black ones.

Sounds like you like to play around with these things. I would be very cautious doing any of the short-cut ideas you may have and think of. You are the one holding on to the step-down handle when you step off the bottom step of the trailer... Learn not to burn or hurt someone else...
Be safe my friend...
Roy Ken