I've got a potential solution.
I know this is an old thread, but I just went through this issue. I'll post my solution in case anyone wanders through here.
I was getting the Device Descriptor Request Failed with the link cable. I powered down and used a regular USB to attach it to an external port, and that worked. So I powered down, switched back to the link that goes to the mobo header, and nothing again. At this point I was a little frustrated, so I thought, I'll just use the external USB to set the RGB color on the damn thing, then switch back to the proper link cable and wait for Corsair to patch it.
This is where I got stupid. Impatiently, instead of powering down my unit, I did the swap with Windows running and Link up. I figured it's just USB, what could go wrong? So I set the RGB color, then switched the cable back to the Link cable. For the record, I DID NOT remove the end of the Link cable from my motherboard. I just had the end that goes into the CPU Cooler removed.
Anyways, after swapping it with Windows on, Link now showed two H110i's. That means it was recognizing my cooler via the proper Link cable. I did a quick reboot, and now Link shows just one cooler, and everything works as it should.
TL:DR - With Windows on, unplug the Link cord from the Cooling unit, and plug in a regular USB cord to one of your external USB ports. Once Windows properly installs the drivers and you see it in the Link software, switch back to the proper Link cable. You'll now see two Coolers in the Link software. Reboot and you're good to go.
