A 'reset' of a 777 (or most aircraft) basically means depowering completely, then bringing it back up from the depowered 'cold' state.
10 minutes sounds about right for doing that.
Educated guess is that they thought they had a 'soft' fault that would be corrected by what is essentially a 'reboot'. But it turned out to be a 'hard' fault that required actual troubleshooting and replacement of the defective box.