HGST 8TB x 2 drives upgrade in G-RAID Removable won't mount macOS High Sierra

I have a G-RAID Removable 4TB (2TB x 2 raid 0) which works fine with Mac Pro 5,1 and macOS High Sierra. I upgraded the drive size to 8TB x 2 using two HGST HUH728080ALN600 4Kn drives. The drives power up just fine, but the G-RAID Media doesn’t show up or mount in Disk Utility. Everything I’ve read says these drives should work. Any help or suggestions on troubleshooting would be greatly appreciated.