I have the  issue. i try and try and try and try to reset factory default and nothing. factory reset fail and factory reset fail. it`s unbealievable what de DJI admins don`t know nothing to do. I must to reset factory my DJI Goggles. I want to use with my Phantom 4 pro with head tracking and i can´t because the goggles are initialize to mavic. i`m sell my mavic and my goggles don´t working property because needed to factory reset default and start again.

I need a solution please. i try in Mac in Windows and nothing. I can´t believe this auction for DJI

Sorry for the trouble caused, currently, it's not supported to reset Goggles to very first time status, "Reset All" is just to reset the settings like brightness, volume, language to default value, but not include the linking status with drone and camera settings.
The issue has been reported to our engineers for assistance, we will come back to you once there is update, appreciate your patience.

Update:After linking the Goggles to Mavic Pro, these two devices will link automatically when both of them are on. The linking priority of the Mavic Pro is higher than the P4P, that means you can't link the P4P via USB cable with the Goggles when it is linked to the Mavic Pro.  
To use the Goggles with the P4P, you need to disconnect the Mavic Pro by pressing the linking button, then connect the Goggles via the USB cable with the P4P.