External WD 1 TB will not connect (mount) on a Mac

I have had this problem for a while where the external WD drive doesn't want to connect or be visible on the Mac. I thought it was the cable and fiddled about with that but no. Occasionally it would connect but it didn't follow a pattern, or didn't seem to. I am using the drive as a Time Machine backup.

I may not have fixed it entirely but I can now get it to mount and indeed it has mounted correctly ever since - a few times.

I went to the Disk Utility app and the 1 TB WD drive was being found. It was in the left-hand pane as  shown in the image below.

The below image shows the drive in its working state.
In it's error state it was displaying the text: disk1s3

I went to the Terminal and ran the command:

diskutil list

This provided me with the following:

John-Mac-mini:Volumes John$ diskutil list

/dev/disk0

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      GUID_partition_scheme                        *500.1 GB   disk0

   1:                        EFI EFI                     209.7 MB   disk0s1

   2:                  Apple_HFS Macintosh HD            499.2 GB   disk0s2

   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

/dev/disk1

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:     Apple_partition_scheme                        *1.0 TB     disk1

   1:        Apple_partition_map                         32.3 KB    disk1s1

   2:                  Apple_HFS                         1.0 TB     disk1s3

I then mounted the drive:

John$ diskutil mount disk1s3

I noticed immediately that the drive mounted on the desktop and in the DiskUtility app.

Note that the disk identifier may be different for your setup. If you are unsure, look at the disk Utility app where I have drawn the red rectangle.

As I say, I haven't fixed this because at the next power off it may refuse to connect again.

When running distil list again the drive partition is given a name ' My Book Time Machine' as expected. I am not sure if this name is only available after mounting, and therefore it is correctly blank before mounting, or whether that is a part of the problem.

/dev/disk1

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:     Apple_partition_scheme                        *1.0 TB     disk1

   1:        Apple_partition_map                         32.3 KB    disk1s1

   2:                  Apple_HFS My Book Time Machine    1.0 TB     disk1s3