My Book for Mac Back Up with Time Machine

WD External Drives External Drives for Mac
2

Hi,

Are you connecting the drive directly to the wall outlet or a power protector? If is on a power protector, try connecting the unti directly to a wall outlet and make sure to test the unit on a different USB port. 

Also, will be good to try transferring some files directly to the drive like drag and drop or copy and past to see if is a drive issue.