Big Sur Thunderbolt 2 - External Drives-not recognized by multiple Macs.

I'm trying to set up a new backup and external drive system for my spouse. She has an iMac Retina which I, fear, I updated to run Big Sur. There are two external hardware RAID drives, a G-RAID configured for RAID 0, and a Brand new Mercury Elite Pro Dual. Each are Thunderbolt 2. The iMac didn't see the drive. I tried the same thing with my MacBookPro (also now Big Sur) with the same result.

Strangely, I could format them both if I attached using USB. but when I went back to Thunderbolt connections, mostly nothing. I could get one to mount on one Mac sometimes. I tried all ports, different cables, and one at a time.

Tried zapping the P-RAM but I guess the old ways are not more. The old key combo didn't work

Help, please