Membership cards are compatible with Apple Wallet and Google Wallet on eligible devices. If you attempt to download your membership card and it does not succeed, it may be because your particular device does not support these utilities.
Make sure you have a compatible device and updated software:
As a workaround, when clicking to download your membership card, you can click the 'Preview' link, then capture a screenshot of your card and save it to your photo library.
On desktop computers, you may also print a copy of your membership card.