Your phone must be connected to the internet to receive the balance or reward updates. Sometimes, mall wifi's prevents points or rewards updates due to their connectivity restrictions. If you have an iPhone, go to Apple Wallet, click on the three dots button in the top right corner of the card, toggle off "automatic updates" and toggle on "automatic updates". This will update the balance on the card. If you have an android, close your Google Pay app and open it again. This will update the card information.