I'm running two Pegasus2 R4s on a win 10 system.

This morning I had a drive fail on the first unit. 

I had a look in the utility and could only see the second unit. I didn't think too much of it, then bought a replacement drive and popped it in. Now I'm getting four blue lights on the front of the unit but it's still not visible on the utility. I've tried using the thunderbolt cable from the second unit (which was still visible) and still not seeing it. 

I tried removing the new drive and putting it back in. Now, instead of all blue lights, I get 4 blue lights for the disks, but an amber light on the power button which changes to red after a minute and then the unit shuts down.

Any help would be greatly appreciated as I have 11 terabytes of data on there that I'd hoped would be safe because of using raid 5

Thanks in advance