From what you’ve said here, there doesn’t seem to be any obvious reason why you are not yet connected to ThruLines, so I would suggest contacting Ancestry support - by phone, if you can.
Before contacting them, though, it is a good idea to sign out of Ancestry, then clear your browser cookies and cache, then log back in. Also try a different browser if you have one. These are usually the first things the support team suggest, so if you’ve already tried them without success, you can quickly move on to exploring things that do help.