I see more people experiencing this issue coming in. Hopefully there will be an easy fix for this because I've tried everything: Hard reset (volume up, down, power button) did not word Holding volume down (or up) and power did not work. Changing usb charging cable did not work. Wireless charging did not work. Connecting it to my MacBook Pro did not work. If you find something please share.

+1 this comment. This worked for me. (Luckily) I connected my iPhone through USB-C to my MacBook. I quickly pressed Volume Up, Volume Down, and Hold the Side button until it became dark. I then hold the Volume Down button and released the Side button after 5 seconds while continue holding the Volume Down button. If you again see the battery on screen you have not counted properly and was holding it to long. I then hold the Volume Down button until my MacBook detected the iPhone in DFU.