One of the simplest explanations that your iPhone isn’t charging could be that the physical connection between your phone and the charging cable or station isn’t solid. Your cable might not be a "certified Apple product" or merely be worn down over time. Also, dirt or dust may have collected around the charging cable's connections or inside your iPhone's connection port.

The easiest solution is to test the software by restarting your iPhone, waiting for it to finish, and then plugging it back in for a half-hour. If that doesn’t work, you can experiment with the physical charging station by disconnecting and reconnecting the cable from your iPhone, the power outlet, your computer, or the charging station. You can also borrow someone else’s cable to troubleshoot.

Even if things look fine, try cleaning off the connections on both ends of the charging cable, and check your iPhone's port for dust, dirt, or pocket lint. You should also inspect the ports on your computer, and carefully clean them if they look dirty or clogged with anything. As a last-resort, you can always call Apple Support if you think your iPhone’s battery is faulty.