unable to add store cards to wallet

Welcome to ASC.

Store cards are generally added via store apps (or sometimes store e-mails linking to a store’s website).

Unfortunately, any issues adding them to wallet will need to be addressed-to, and resolved-by the store’s app developer.

Get more help and assistant from Apple directly, see Contact Apple for support and service -> Contact Apple for support and service – Apple Support (UK) 

The message is clear.

Check with the shop where you purchased Advantage card.