Can't add card to Wallet app, there's no + button.

Welcome to Apple Support Community!

If you do not see the + option in wallet, that could indicate that your device country or region is not set to an eligible country.

If you can't add cards to wallet : https://support.apple.com/en-us/HT205630

Review this resource for eligible country or regions for Apple Pay https://support.apple.com/en-us/HT207957

You may change your device country or region by completing the steps below:

1. Settings
2. General
3. Language and Region
4. Tap on region and select eligible Country or region

Hope this helps ;)

👉🏼 You need to turn off Airplane mode. 