The guy that comes by the house to fill my 500 gallon tank also checks my coach to see if needs filling at the same time. He uses the same adapter for the coach as he does for the house.
A good propane supplier will have multiple adapters on hand to fill tanks with different fittings. A supplier I used a couple of times for my Class C had to change adapters on his hose the first time he filled that coach. Had the same issue as you when he could screw on the adapter but the tank wouldn't fill. He screwed another adapter on his hose and all worked fine. He had about 5 different adapters for his filling operation.
US Army (Ret)
2020 Entegra Accolade 37TS
2019 Jeep Grand Cherokee Trailhawk (Toad)
FMCA - F432054