I have a late 2015 27" iMac running Sierra and the latest updates. I have a Western Digital MyBook USB3 4TB drive running time machine. It has worked flawlessly for 15 months. Then last week I got a message that the backup failed. The message was "Unable to complete backup. An error occurred while creating the backup folder." After some trouble shooting and a waist of a half a day and also trying everything google had to offer. I gave up and reformatted started over. That worked fine for a week and today I get the same message. I checked the drive out with disk utility, and DriveDX, and everything looks good. I thinking it is a permission error because of the red no symbol on the folder. I just can't trace the cause. I usually let my mac sleep when not in use but once in a while I shutdown today and last week were one of the times, so for some reason shutting down may trigger this. Any suggestions will be helpful.
Thanks
Thanks
