This really sounds like an AM problem to me. CO/DL/NW recognize my ST EP status without any problem. If your mother in law could select priority seating and you could not, there is something wrong. Especially considering that you have this issue with more than one airline, there must be something wrong with the AM database. I once had an issue with CO which was easily solved by calling them. If you are really desperate for AF priority seating, I would try to fax a request to your local reservation office with a copy of your card/statement. If I were you I would call AM over and over again and have them fix the problem.