Working RAID 5 shows as "non-raid" in SoftRAID 6.2.1

I've been using SoftRAID with an old (circa 2014) Thunderfury 4 enclosure, currently connected to an iMac Pro via an Apple Thunderbolt 2->3 adapter.  It's never had a problem until the last week or so when a disk began to fail, so I've never really looked at the array in SoftRAID on the iMac Pro until the error started to show up in SoftRAID monitor.  The array works just fine as far as I can tell, but shows up as "non-RAID" and I was unable to remove or add disks from the array (selecting the array from the right panel also doesn't "connect" it to the component disks on the left).  Fortunately we had an older computer around with a Thunderbolt 2 port, and after moving the software and array there everything showed up as expected and I was able to use SoftRAID normally to replace the disk and rebuild the RAID 5.  Moving it all back to the iMac Pro the array showed up as non-RAID again, although it is working fine and SoftRAID Monitor seems happy with it - but I would still like to be able to diagnose/fix the array in the future without moving to the older computer (which we plan to give away).  I checked under System Information and the SoftRAID 6.2.1 driver shows as "Loaded" (I've tried uninstalling/reinstalling the driver to no effect).  Is this somehow an issue with the Thunderbolt 2->3 adapter?  Has anyone seen/resolved something like this?