Target not available

After years of successfully using WD Backup, I noticed that for the last 30 days it has not succeeded; gives an immediate ‘target not available…’ This is version 1.9.6485.41934

In Windows (10) Explorer I can view the target drive (4TB, 370 GB available). I can open files on that drive.

But WD Backup won’t back up.

Hello,

Please refer to the following KBA article: https://support-en.wd.com/app/answers/detail/a_id/7755/