help! unable to fill propane tank in rv

I may not understand the issue. I have a 92 Eagle and they had trouble filling my tank. No one knew how anymore. There was a button underneath they had to push before the tank would take propane, otherwise it wouldn't flow. The older guys were familiar with it, it was on old rigs, but it got to be a real issue finding someone that could do it. So couple years ago in Orlando I found a private shop that would empty my tank, put on a new valve that is like what everyone uses now. A plus was they had to recertify the tank, we were concerned they might have to replace it, but the shop guy said that was very rare. They recertified, I now have a valve that anyplace can fill and all is well. I was also happy to know my tank was safe too. They said anytime they do something like that they have to pressure test the tank to make sure its ok.
Just throwing this in, in case it might pertain to you.