External Thunderbolt drive won’t mount

Scott F wrote:

The hardware:

...It is spinning sporadically, it sounds like a child snoring. Buzz. Pause. Buzz. Pause. In about a three second cycle.....

This sounds very much like a hardware failure. It could be as simple as the adapter or the cable or it could be that the drive itself is failing. Both the adapter and the older Thunderbolt cables have active electronics in them which could possibly fail.

I assume you have switched ports on the MacBook Air and get the same results?

It seems like an hardware issue with the drive to me I am afraid if disk utility also does not see it