Some additional details, as I educate myself on TBT3. When I run the Thunderbolt software and plug in the TBT3-UDZ, it does not recognize it as a Thunderbolt device and does not appear in the list. It is probable that I have never plugged a Thunderbolt device into this laptop, as nothing appears in the software, not even the Port name. In the Bios, I can choose between Legacy, Unique ID, One Time Key (or something like that), or DP. I have tried all of the first three, with no luck. The bios is old, so I have asked the manufacturer if there could be an update, but have not heard back yet.
Bottom line, the computer is not able to tell that this device is a TBT3 device, and I can’t figure out why or what I might do to remedy the issue.