I am running Tahoe 26.2 and I cannot mount any longer my TimeMachine external disk, which is encrypted, although I am sure the password is 100% correct. I tried with Disk Utility even to erase the disk in order to restart from scratch but it refuses, saying the password is incorrect. It was working perfectly fine 2 weeks ago with the former MacOS. Any hint what is wrong or what to do?
phicharp wrote:
I tried with Disk Utility even to erase the disk in order to restart from scratch but it refuses, saying the password is incorrect.
There should be no need for a password to erase the drive even if you are just erasing the encrypted volume. However, I always feel it is best to erase the whole physical external drive as outlined in the following Apple article (I find this older Apple article archived by the Internet Archive is an easier to understand version than Apple's current version of the article):
FYI, if you receive a prompt to authenticate when first launching Disk Utility, then that password prompt will be for your macOS admin login password. We have no idea why Disk Utility is sometimes prompting for a password when Disk Utility is being launched.
phicharp wrote:
I tried with Disk Utility even to erase the disk in order to restart from scratch but it refuses, saying the password is incorrect.
There should be no need for a password to erase the drive even if you are just erasing the encrypted volume. However, I always feel it is best to erase the whole physical external drive as outlined in the following Apple article (I find this older Apple article archived by the Internet Archive is an easier to understand version than Apple's current version of the article):
FYI, if you receive a prompt to authenticate when first launching Disk Utility, then that password prompt will be for your macOS admin login password. We have no idea why Disk Utility is sometimes prompting for a password when Disk Utility is being launched.
There were a few prior posts on this forum from users who couldn’t access their external drive due to the drive manufacturer’s software that they used to encrypt the drive. Lacie/Seagate, Samsung, SanDisk, etc., all provide 'drive management' software on their drives and using such 3rd party software can cause issues when macOS is updated and the 3rd party software becomes incompatible. Not sure if that's the issue here, but FYI the best practice with a new external drive (SSD/HDD, not applicable to NAS drives) is to use Disk Utility to complete erase it, format it as GUID/APFS and apply encryption if desired.
External TimeMachine disk not recognising password
