I have a new Time Machine Backup which was just connected 2 days ago. I wrote down my password. I had to disconnect yesterday to add a thumb drive for a document but now the Backup will not accept my password. What to do?
Mac mini, macOS 15.1
Erase the backup drive. There is no need nor is there any benefit to separately encrypt a TM backup drive. Just select the option to encrypt backups when adding that drive to Time Machine.
Back up your Mac with Time Machine - Apple Support
The bullet point under Step 4 explains.
By the way, it's not a good idea to write down passwords, not even on a piece of paper that you subsequently and immediately destroy.
My Time Machine backup disc (LaCie) will not accept my password
