My daughters has the same thing happening to her "a valid adult pass is required to book this offer".
She has not renew her AP or anything as her AP is good until July at which time she will have to renew.
She called Disney and they told her they are having alot of trouble and a lot of people are getting the same message as you are.
They told her to try another AP pass holder in the family to see if any of them are working, but of course all the rest are children.
So far my AP pass is working so I can look on line, but once June hits, which is next month, I will have to renew mine and of course I maybe facing the same thing as others have.
Disney did say they were trying to work on and but so far no go!