You Can’t Wirelessly Charge a Cable-Connected iPhone
As Apple warns, if your iPhone is connected to a USB connection, it cannot wirelessly charge. Instead, it will automatically charge using the cable connection, and the wireless charger will not be able to connect.
This may be an issue if your iPhone is connected to your MacBook or a battery pack, and you want to save the battery charge in those devices by using wireless charging instead. Just note that you can only charge your iPhone using one method (or the other) at any given time.