Back in March, Google began notifying Google Wallet users that the physical Wallet Card was on its way out. The card would continue to work normally until May, after which it would no longer be possible to top it up with funds from a bank account, and on June 30th, Wallet Card would be officially retired. Unfortunately for the dozens of customers who signed up for Wallet Card, that day has finally arrived.
Like so many Google products before it, Wallet Card was a nice idea that never garnered enough users to justify Google's time and resources to back it up, lasting less than 3 years from launch to shutdown. After today, any transactions users make using the card won't get processed, so you should update your payment method if you're currently using Wallet Card for any kind of automatic payments. On the other hand, there's no need to spend any remaining funds you may have left on your card since those are still linked to your Google Wallet account, meaning that you can easily transfer any money to a linked bank account or debit card.
If you're one of the few people that used Wallet Card on a regular basis, Google recommends looking into alternatives like Simple or American Express — they've even teamed up to offer Wallet Card users a small bonus for signing up.