How to reset or initialize the Wireless Headphones (WH-1000XM4)
Reset the Headphones
Plug the USB cable into the headset to charge.
Press the POWER Button and the CUSTOM button at the same time while the USB cable is still connected.
The headset will reset. To charge the headset after resetting, disconnect and reconnect the USB Type-C cable.
Initialise the Headphones to Factory Settings
Turn off the headset, and ensure no USB cable is connected.
Press and hold the POWER button and the CUSTOM button for 7 seconds or more. A blue indicator light will flash four times.
The headset will initialise, resetting the settings and pairing information.
Delete the headset from the list of Bluetooth products on your device.
Pair the headset to your selected device again