I have never seen Thunderbolt damaged "from usage". We have had machines doing heavy IO for 3 years on 16 drives (in testing), no issues.

Here is what you can try next:

Do a clean install.

Run Disk Utility.

Click on your startup drive and click + on the upper menu, by volumes.

Create a new volume. This will be APFS, so it shares your volume space and does not affect your existing volume.

Startup with Command r on intel, or, the power button on M1 for options.

"reinstall mac OS" and install mac os onto it.

Use your same admin account name for simplicity

Now see if thunderbolt is working on that.

If it is not, then backup your main system and bring it into Apple.

If you think it's a hardware issue, then there's only one possibility, and that's that the controller on the Logic board is fried. I really don't see any other option than to backup this machine, do a fresh reinstall, and and take it to the Apple store. I guess what I need to know from you guys is whether or not the Thunderbay can cause this kind of damage by leaving it on for extended periods of time, or keeping it plugged in while the computer is sleeping, or whatever. The thunderbay was working fine on this computer for about a month and then I woke up one morning to find it inoperable on this machine. 

Do you have access to any other Thunderbolt devices?

Note if you connect a device, it should show up in System Profiler (about this mac), under the Thunderbolt tab on the left column.

You said you tried the other thunderbolt port, correct?

I cannot guess yet what is actually going on.

 - It is indeed a thunderbolt 3 cable

I did understand this is what you are dealing with, but its still a hardware issue of some kind.

(If the disks showed up, but SoftRAID could not mount them, then it is a software issue. the fact that they do not even power up, demonstrates this is something about the hardware)

Send me a SoftRAID support file with the SSD connected to the iMac and another with the array connected to the Laptop. that will tell me what I need about both.

Also let me know if the cable has a "3" on it, a "lightning bolt" icon, or nothing, stamped on the ends.

I saw the SSD is in a USB 2 enclosure, not sure if that meant anything yet.

I made you a quick 1 minute video to clarify what's going on: https://www.youtube.com/watch?v=2fZPxpcv-w0

This is a hardware issue, it is a matter of figuring out the cause. Here is what System Profiler sees on your system.

Did you try the other port on the computer?
If the unit is currently connected, for some reason, the M1 does not think it is.
When you plug it in, do the drives spin up? Then at least you know the Thunderbolt signal is reaching the enclosure...

I'll try again. We can with total confidence exclude the possibility that this is cable or hardware issue because:

1. Other drives plugged in to the same ports with the same cable work on the iMac

2. The array in question that isn't read on the iMac IS read on another machine using the same cable.

3. I've tested this upwards of 30 times with 100% consistency

Did you have the disks connected when you saved the support file?

If not, save another with the disks connected.

If they are, then this is a hardware issue, cable or something.