I'm running Windows 10 1909 and MC 2021.9 with a Nitris DX.  This seems to be the last stable software combination for the Nitris before support was dropped.

Windows auto-updated without my knowledge over the holidays.  By the time I discovered that it had, the restore point had already been deleted.  So last week I did a clean install of windows and MC.

Yesterday I was working remotely and disconnected the Nitris.  Today, I discovered that MC will not reconnect:  clicking the HW/SW button does nothing.  A restart did not help.  The configuration tab shows that the Nitris is available.

Any help is much appreciated!

UPDATE: The only solution that worked for me was to wipe my system and reinstall windows 10 1909, MC 2021.9, and the Nitris driver.  Luckily I had saved a windows install USB and all my app installers after the last wipe, so it was a pretty painless process.  Highly recommend throwing all your installers on a drive as backup...

What does your Nitris do when you re-install the DX driver?

So when I use the driver installer to deinstall it, Media Composer interestingly still shows the Nitris as available.  Reinstalling didn't fix the issue.

I next de-installed the driver again, deinstalled MC, reinstalled all, and still no luck.  I also created a new user and project just in case.

many many moons ago in ACSR class, when the DX hardware was just released, I proved to avid that disconnecting the DX hardware via the system try would sometimes result in BSOD, and other times require the DX hardware to be fully power cycled: full computer shutdown, unplug DX from power, hold down power button for up to 30 seconds, then plug back in and reboot computer.  

this may resolve your connection issue. it may not. but it sounds like it's worth a shot if you have someone available to get hands-on. 

No luck unfortunately.  When MC is running, the Nitris shows the following:

Host link: solid green

Sync: blinking orange/green

LTC: blinking green

Audio: solid green

Analog: solid orange

SD SDI: blinking orange/green

When you right click the HW/SW button, is the Nitris DX an option? A check mark is active?

When I right-click the button, I get the standard timeline right-click menu.

Update:  I was able to reconnect the Nitris by wiping my system and reinstalling windows 10 1909, MC 2021.9, and the Nitris driver.

Still not sure what the issue was, though I suspect it had something to do with the driver, since even after de-installing it, MC still showed the Nitris as available.  

Thanks for informing us!