Received new replacement passport for Mac. showed up right away on my desk top. I need to reformat it using disk utility so I can back up my computer, but I get this error 69888 unable to unmount disk. I cannot yet find answer how to fix this. Please advise.
I found the fix on the Apple community and it did work for me:
This should work;
1 Turn off the Mac
2 Turn it on, and immediately press and hold Command + R until you see the Apple logo.
3 Once in macOS Recovery, choose to Disk Utility. [There
are a number of other choices… ignore those]
4 Select “View” > “Show All Devices” in the upper left corner of utility
5 IMPORTANT: Select the disk in the side bar External Section, NOT Internal.
6 Click Erase, and use APFS and GUIDE if it is Big Sur or later. If earlier
choose one “extended” below it.
7 Click Erase again.
8 Once done, click the Apple Menu (top left) > Restart. This will put you back into macOS.
