Passing this along in case other users run into the same problem. A few days ago my Quantum 2626 suddenly stopped working. My computer (ASUS laptop) wouldn't connect to it and I had the dreaded steady red light for synchronization.

I contacted Presonus support and they ran me through the usual list of scripts to no avail. Kept having me uninstall and reinstall Universal Control even though it never worked. I asked them if it might be a Thunderbolt problem since Windows 10 just did a major update a few days before the connection was broken but they seemed to ignore that suggestion.

Late last night I started poking around and came across this Intel website. I downloaded the new Thunderbolt driver and wouldn't you know, my Quantum 2626 came back to life! Working like a charm now.

So if you're having an issue where your Quantum suddenly won't connect and doesn't show up in UC, try this download.

https://www.intel.com/content/www/us/en ... 11ebv.html?