- Please watch the upper ☝︎ video carefully and follow the steps. (in case the video doesn't work, press on this link)
How to fixed this:-
1) Force an External Hard Drive to Mount via Command Line Terminal.
2) mount_apfs: volume could not be mounted: Permission denied.
3) How to make root volume writeable in Big Sur?
The code used in the video: -
sudo diskutil mountdisk disk1s5