Size is less... for GPT disks

I have the MediaSonic enclosure model: HFR2-SU3S2. It was just purchased new. I am using 4 -- 6TB HGST hard drives and have the unit set for RAID 5 while it is plugged into my Windows 10 64 bit computer.
I also have a MediaSonic ProBox with the same hard drives, running a RAID 5 and has had no problems!
This is actually my second MediaSonic enclosure model: HFR2-SU3S2. I sent the first one back because I could not solve the problem, I thought it must be the controller card in the unit. But I am having the exact same problem with this second unit.
I set up the four drives into the unit and follow the MediaSonic manual to create a RAID 5. Then I go into the Windows 10 Disk Management program which immediately recognized the one RAID drive. However, it shows up as "Unknown" and when I try to initialize it I get this error message: "the specified disk is not convertible because the size is less than the minimum size required for GPT disks."
If I was to run a RAID 0 or 1 it would work. But it is the same problem for RAID 3 and 10.
Do you have a suggestion for how to fix this problem? One other thing I have done is -- I took each drive into my computer and used Diskpart to clean each drive. So each drive should have nothing on it when building the RAID 5.
I also have a MediaSonic ProBox with the same hard drives, running a RAID 5 and has had no problems!
This is actually my second MediaSonic enclosure model: HFR2-SU3S2. I sent the first one back because I could not solve the problem, I thought it must be the controller card in the unit. But I am having the exact same problem with this second unit.
I set up the four drives into the unit and follow the MediaSonic manual to create a RAID 5. Then I go into the Windows 10 Disk Management program which immediately recognized the one RAID drive. However, it shows up as "Unknown" and when I try to initialize it I get this error message: "the specified disk is not convertible because the size is less than the minimum size required for GPT disks."
If I was to run a RAID 0 or 1 it would work. But it is the same problem for RAID 3 and 10.
Do you have a suggestion for how to fix this problem? One other thing I have done is -- I took each drive into my computer and used Diskpart to clean each drive. So each drive should have nothing on it when building the RAID 5.