Well, I think I found the solution after 2 weeks of trying. In Pete’s Discord thread, I found a link to a thing called midifxreg.
I ran this and I re-installed the CC121 drivers, and plugged the CC121 back in, and I believe Cubase was now able to find it!
I now see this in Cubase:
This is a major breakthrough! The blue led light is now steady (not blinking). I will now have to start re-installing everything I disconnected to see if it is really working. I am so happy! Thanks zero zero!
@Realist , even though the problem with the CC121 seems to be resolved and it may have not been related to the Korg drivers, I went into regedit and didn’t find any instances of the word Korg in the Drivers 32 folder that you show in your screenshot. However, I happened to notice a KORG folder under HKEY_LOCAL_MACHINE\Software\
I didn’t do anything with that entry but Im wondering if I should delete it.
Thanks,
Chris
But you did do something, didn’t you?
You ran Pete’s midifixreg tool. That repaired your registry. 
I was specifically referring to the registry entry I mentioned, not to any other folders.
That’s absolutely fine.
I just didn’t know your current situation, and I didn’t know you were also active on Pete’s Discord channel.
If any problems crop up again, I’d advise you to ask Pete directly on Discord. He’s very active there and replies fairly quickly.
In any case, I’m glad it’s sorted now.
You need to leave Developer Mode on for as long as you have a preview service plugin installed. Otherwise, the service is not going to load that plugin. If you turn off developer mode, the next time you start/restart the service, or reboot the PC, the plugin will not be loaded.
Pete
Microsoft
As Realist said, that’s the tool he was referring to for fixing registry problems caused by the Korg driver installer/uninstaller.
Now that Windows MIDI Services has been fully rolled out, we’re strongly considering just having Windows force those entries to be present starting with an upcoming update. I don’t like forcing things like that, but we’ve had so many problems from the Korg driver uninstaller/reordering, that it’s going to be the lesser of two evils by a long shot.
Here’s the technical article that tells you what’s required.
Pete
Microsoft
Just for info
Latest Cubase pro and latest windows 11.
CC121 working fine.
Also, working well with Ableton Live 12
