Oh, I have had a lot of experience with this valve in our previous coach. I won't bore you with the details. However, if it really will not turn you do have a problem as mentioned previously by another poster.
Google "Anderson Brass Company" and you will get their website. They were very helpful each time i contacted them with a problem. They are just outside Darlington SC.
Good luck. I wasn't overjoyed to see it in the our new RV but hopefully it will go smoother then with the previous RV!