WD My Passport Ultra - Not Enough Room?

The drive says there is 3.63TB out of 3.63TB (4TB Drive) available but when I run WD Backup and point it to a drive that is 2.72TB in size, the WD Backup program complains and says:

Unable to back up files to My Passport Ultra because there is not enough space.

The 3TB external drive I am trying to back up has 388GB of free space.

Any idas?


Have you tried uninstalling and reinstalling the software?

I have yes.
I’ve also quick-formatted the 4TB drive.