Can't re-connect My Book for Mac

I connected My Book for Mac for my Time Machine and the computer made a back-up to the drive. But the next time I logged on to my computer it doesn’t see the drive. The drive is actually listed in the Time Machine Backup Disks, but it is not in the “Available Disks” section so it’s no available for back-up. Can you help me? 

Check if the drive is recognized on the Disk Utility app so you can run a test. Check the link below for the steps. 

How to test a drive for defects or problems on a Mac 

Unfortunately, the drive is not recognized. :frowning:

Any other suggestions?

I have the a some what the same problem and the only way I get the External hard drive back on line is to disconnect the usb cable and the re-insurt the usb cable ?