Mounting and Unmounting Repeatedly

I’ve been a long time Drobo user. Had a gen 1, then a gen 2 and now I’m trying to upgrade to a Gen 3.

Other details:
Mac Pro
OS X (10.8.3 or whatever it was)
USB port on rear of computer

I bought a gen 3 and noted that I had a hell of a time getting it to mount the first time to make sure the firmware was up to date. Took about 5 restarts and a bunch of work to get it to finally show up.

Finally did. Then I moved the disk pack from the Gen 2 and it took awhile and everything looked great.

Except now it is unmounting and mounting repeatedly. The Gen 2 sits on the same computer with its own pack of drives and works like a charm. But the 3 goes up and down and up and down.

So I bought a new SSD and installed a fresh copy of El Capitain (been meaning to do this for a while). Same problem. Gen 2 is bullet proof. Gen 3 mounts/unmounts.

I bought a Sonnet USB 3 Card for the PCIe slot to isolate it and get better performance.

Same thing.

Dashboard and firmware are up to date.

So I sent the first Gen 3 back and got a second.

Same thing happens.


Any ideas?