iPhone 11 Pro Smart Battery Case wont charge!

Just bought a brand new iPhone 11 Pro battery case from Walmart. Has never been used nor opened. I put it on my phone as soon as I got it and noticed it had 0% battery right away. I then plugged it in to charge. After 9 hours on one of the 20 W charging bricks that is an official Apple product, it still has 0% battery. I’ve tried several outlets, several cables, and several configurations between my phone and the case. What do I do?