3620 - 8tb disk size support - bios does not recognise 8tb disks.

Hi, 

I got hold of the 3620 as a replacement to the microserver and am in progress of moving my data. So far all works better than expected (like power consumption - 25W-ish, wow!) except the 3620 failing to see any of my 8tb disks. I can see 2tb using same data/power cables no problem, but none of 8tb. The large discs are working fine in the microserver. I had a decent search through the forum and was expecting it to work straight away. I got the latest bios, tried multiple sata ports. 8tb discs are not recognised in bios no matter what I do. Not to mention obviously these are not recognised by the system after. 
Have I missed any bios settings or are there any special requirements needed for it to work? Seen a topic about pci sata card being needed, but its mixed up with confirmation of support for the 3620 for any disk sizes, so I am a bit lost The system is installed on the nvme, but I had an issue with 8tb's before I installed that disk as well.

Many thanks!

Max