We are sorry to hear that your unit is not as intended and we will try our very best to troubleshoot the issue with your product. In order to further assist you, we'll need to know a bit more information and have you run a few tests for us to verify and eliminate the given possibilities.
-For the MB561U3S-4S R1 being used on the Mac computer, did the unit work perfectly fine before the update to High Sierra? YES great
-What drives are you using with the units? Please provide manufacturer, model, speed and capacity.
WD 1.0 TB SATA 32 mb model WD1001FALS (7200RPM) haven’t tested in internal slot
TWO Seagate 3TB BarraCuda ST3000DM008 (7200 RPM) haven’t tested in internal slot
Seagate 2000GB (2TB) ST2000DM001 (7200 RPM) may have failed but not in use or inserted
-Have you confirm the drives are working fine outside the unit? see above…not yet
-How are the units connected to the computer? Ideally, they are connected to a port on the computer, not through a hub.USB 3.0 directly to back of computer…but I could hook up eSATA…have cards to install
-Have you tried using different cables and ports on the computer? It is possible it is related to those parts. I had changed Ports….not the USB cable yet