Apple:

Apple has determined that some Smart Battery Cases made for iPhone XS, iPhone XS Max, and iPhone XR may experience charging issues. An affected Smart Battery Case may exhibit one or more of the following behaviors:

• Battery case will not charge or charges intermittently when plugged into power
• Battery case does not charge the iPhone or charges it intermittently

Affected units were manufactured between January 2019 and October 2019. This is not a safety issue and Apple or an Apple Authorized Service Provider will replace eligible battery cases, free of charge.

If you have the battery case for any of these three affected phones, contact Apple about getting a replacement.