Time Machine not working

The Time Machine is suddenly not working on my MacBook Pro, already updated OS to 10.14.4. When attempting auto or manual backup i get the message "...There was an error while copying files". I have run disk utility first aid on the external backup disk and gave no errors. I have deleted the com.apple.TimeMachine.plist file and rebooted Time Machine and selected drive again...same error. I have restarted the Mac numerous times at different stages and have tried command+option P R. I purchased a new external drive (Seagate Backup Plus Slim for Mac) and tried with this and am getting the same error on the new drive. I ran disk utility first aid on the new disk and no errors present.

**Any Ideas??**