T2 issues with G-Raid on late 2015 iMac

I have been using my 2 4TB G-raid drives without issue for a few years and recently they began to unmount themselves for no reason. Now I cannot even mount them.
Both drives work on my MacBook Pro (with T3/T2 adaptor).
I have a 2nd Apple Monitor connected to the T2 drive on the iMac and it works well.

Suspect a hardware problem on the iMac but can’t figure it out!

You should try contacting WD’s Technical Support about this for live assistance and troubleshooting

To Contact WD for Technical Support

support.wdc.com