Whatever has gone wrong, the card page itself is their card: it has the code you scan and the running count. Adding it to a wallet is a convenience, not the thing.
They tapped Add and nothing happened
Ask them to go back to the card page and try once more. Some older phones and some in-app browsers, the ones inside a social app rather than the phone’s own browser, will not hand a pass to the wallet. Opening the same page in Safari or Chrome usually settles it.
They closed the page and lost it
They scan your QR code again and sign up with the same email address. LoyalPack recognises them and takes them straight back to the card they already have, stamps and all. It does not create a second card. If your Program does not collect an email address, there is nothing to recognise them by and they get a new blank card instead.
The camera will not read your code
Ask them to turn their screen brightness up and hold steady for a moment. If it still will not read, your sign-up link is ordinary text: read it out, write it down, or send it to them.
None of this loses anything. A customer who joins now and adds the card to a wallet next week keeps every stamp collected in between.