My Pegasus2 R4 is acting up.

I use it primarily as a workdrive for professional photography on an iMac running macOS Cataline (10.15.7).

Yesterday went to import a shoot via Lightroom (onto the Pegasus). Then started getting alerts from the Promise Utility Daemon (see attached):

"Promise Utility needs your attention
There has been a Minor event on Pegasus2 R4"

Looking at the utility (see attached) and crossreferencing online it appeared the error ("Command times out on physical disk") was on PD 3 and that the best solution would be to replace the drive. Ordered a new one to pick up it the morning, shut down the iMac.

This morning awoke to see that the Pegasus itself was still on. Powered on the iMac but the drive wouldn't appear on the desktop and didn't appear in the System Information utility under Thunderbolt. The drive lights were all blue with an orange power button.

Disconnected the Thunderbolt from the iMac, the power cord from the Pegasus, powered down, waited 5 minutes, powered back up, reconnected. The orange light was gone, I could see the Pegasus in System Information under Thunderbolt but the drive itself wasn't accessiable/visable in Finder.

Since this morning the Promise Utility will open but no windows appear.

In reading threads on here appears it might need a new inclosure or perhaps to try it on another machine. Getting a USB C to Thunderbolt adapter to try on my laptop later this morning and have put a formal ticket in on the Promise support site but have heard mixed reviews on the speed of reply.

Thankfully have all of the files also backed-up via Backblaze but want to:

a) See if I can get this Promise to work.
b) What the best replacement option would be (they don't seem to sell the R4 anymore)
c) I'd like to get back to work.

Thoughts?