Do you already have your MP card in Wallet? IME, it will only show as an option if you don't have your current MP card in there. If you do, it won't let you add it again (or to update).
Also IME, in the past, if you had an 'expired pass' in there, the icon would show to get a new one. I'm no software developer, but I imagine the API would allow them to disallow that if they wanted.