A dryer receptacle is a 240V receptacle, with two hot leads (240V line-to-line, and 120V line-to-neutral on both legs), a neutral and a ground. That would not be friendly to your typical 50-30 converter devices.
Your typical 50-30 converter is a 110 V only device. It should tie the two hot legs of your coach power cable together, and carry them through to the single hot leg on the male side of your converter. The neutral leg and ground leg of your coach power cable should pass directly through to their respective legs on the male side of your converter. That way, your ground and your neutral come through, and both of the 110V legs in your coach are fed from the 110V leg on the 30 amp supply.
If you have a multi-meter, you could de-energize the 30 amp receptacle with its circuit breaker. Then, using the voltmeter function, VERIFY that there is NO voltage to the cabinet that the receptacle is mounted on or in, from any of the receptacle terminals. If all three terminals show zero volts, AC, then put the meter into the ohms mode, and check the resistance to the cabinet from all three of the receptacle openings. You should see an extremely high resistance on the terminal that is the hot leg, and nearly zero resistance from both of the other two. If the center lead does not show essentially zero resistance to the cabinet, the open ground is in the panel. If it does show essentially zero resistance, the problem could be in the coach power cable, or the incoming connections in the coach.
In any case, in other than a campground power pedestal, before using any adapters, be absolutely sure that your connections will be compatible with your coach power cable configuration. Consult a qualified technician or electrician if you are at all unsure.