This usually happens when you log in with a new login option. Make sure you logged in with the same option you previously used: phone number, Apple ID, Facebook, or Google account. Your wallet and all cards should be linked to one of these options.
If you logged in with the right option but had previously reinstalled the app or changed your device, then just wait a little bit — your cards should start loading automatically.
If nothing helps and your cards are still missing, reach our support team and describe your issue in detail:
in-app chat (the "Chat" tab in the bottom navigation bar)
in-app contact form ("Menu" → "Contact us by email")