Having a very similar issue with a G-RAID Thunderbolt 3 16TB I purchased a few days ago.
I had upgraded to Mojave version 10.14.6 even before attaching the device for the first time, and there are no adapters involved as the drive is directly connected to an iMac 27" 2019 with a Thunderbolt 3 port.
At first the Configurator (version 1.1 (52)) recognised the device and I was able to set it to from RAID 0 to RAID 1 mode. Then, after I formatted it with Disk Utility (to Mac OS Extended), the system recognised it as a 8TB drive, as expected, and Time Machine was able to run backups on it.
But the Configurator then stopped recognising the device (even after many prolonged attempts, leaving the Configurator open for quite a long time) - it constantly gave “No devices found”. As a result, I was unsure whether the RAID 1 was indeed working (i.e. whether the data was being written simultaneously to both hard disks inside).
I wanted to check whether the Configurator would recognise the device if one of the two hard disks was out. I dismounted the device from the computer, disconnected the Thunderbolt 3 cable, powered the device down, disconnected the power cable, and pulled out one of the hard disks. Then connected the device again, with only one disk inside it, the Configurator still did not recognise it.
I repeated the dismounting and power-down sequence, and put the second hard disk back in. Then, however, its LED indicator went red (and so did the G-shaped LED on the front cover), and both remained so even after I swapped the two hard disks (top and bottom), to ensure the issue was not power-related.
An erase of the hard disk via Disk Utility (it is now empty) did not change anything in that respect. But then I pulled out the hard disk with the blue LED, and the one with the red LED went back blue, and displayed all the data from before the erase - which means that it had not failed, and that the most likely source of the problem is (as suggested by Rydia in the 21 November 2018 post) the two hard disks’ being out of sync, or some sort of controller failure or fluke.
In this situation, I would follow Rydia’s advice (from the same post) and use the Configurator to set the device back to RAID 0 and then again to RAID 1 - but cannot, as the Configurator is still not recognising it. Tried connecting it via the USB 3.0 cable rather than the Thunderbolt 3 one, and the situation remains the same.
Any suggestions, apart from waiting for an update to the Configurator?
Thank you very much in advance.