Hi clarklc1,

When you say stopped working, do you mean that they do not recognise if anything has been connected? Is it all the USB ports that are affected? Do they still have power? Do all the other ports on the dock work?

Try powering off the dock by disconnecting the Type-C cable and then removing power adapter from the dock. Then power on the docking station by connecting the power adapter to the dock before reconnecting the Type-C cable to your computer.

Did you happen to install Citrix Receiver last week?  If so there's a known incompatibility with older versions of that application, so you have to make sure you're using version 4.9 or above; Dell has a KB article about it that includes a link to download a newer version.  If that's not it, do you see any devices showing errors in Device Manager, particularly in the "Universal Serial Bus controllers" section at the bottom?  If so, what is the detailed error message when you double-click the device(s)?

Just for the sake of completeness, try manually downloading and updating the ASMedia USB Host Controller driver from support.dell.com, since that's the driver that controls the TB16 dock's USB ports.

I did not install the Citrix Receiver. No errors on the Device Manager. I've downloaded and installed the ASMedia USB Host Controller driver from support.dell.com several times.

The Thunderbolt software icon only shows after you manually launch it; you should see it listed in your Start menu if you want to launch it, but that's not required in order for Thunderbolt to function.  The displays wouldn't be working either if Thunderbolt was down entirely.  When you have the dock connected do you even see the ASMedia USB Root Hub listed in Device Manager?  I can't remember its exact name, but it definitely contains "ASMedia", because the other one pertains to the hub built into your PC to handle its own USB ports.

None of the USB ports on the dock function. The monitor ports are working. I've powered down the dock and reconnected it several times. I cannot see the Thunderbolt Doc icon/app in the tray.

I do not see the ASMedia USB Root Hub listed in the Device Manager. When I launch the Thunderbolt Software I get the following error message: "Thunderbolt Service cannot be found in Services. Please reinstall the Thunderbolt software package.

Interesting.  Well if you open up Services (WinKey+R, then type "services.msc"), is the Thunderbolt Service in fact missing?  On my system it's there and the startup type is set to Manual, I assume because it only starts when a Thunderbolt device is connected, but I don't have one handy.  If yours is simply set to Disabled, try changing it to Manual.  If it's gone, I would suggest disconnecting the dock, uninstalling the software, and then reinstalling it.  At that point you MAY have to reauthorize the dock the first time you connect it, but if so you should be prompted for that.  If it still doesn't work, try installing the Thunderbolt firmware, which requires you to be running the latest BIOS and Thunderbolt software first anyway.

I'm having the exact same situation. I've had a Dell TB16 running for several months, used with my XPS 15 9560 laptop. I have a Dell 27" monitor plugged into the dock, as well as an external Logitech webcam plugged into one of the TB16 USB ports. They both worked perfectly until a few weeks ago. Now, the monitor still works perfectly...but the USB ports on the TB16 seem to be dead. I can move the plug from the webcam to either of the TB16 USB ports and get no response -- no device shows up in Windows device manager, and Logitech Gaming Software doesn't see the webcam. However when I plug the webcam's USB connector into the XPS 15 laptop itself, it's immediately recognized again.

I've disconnected the TB16 and laptop, power cycled the TB16 and laptop. Updated all the drivers on the laptop as per Dell support.

I DO see that the Thunderbolt Service on the laptop is not running. It's startup is set to "manual", and when I try to start it, it will NOT start. No idea if this is related to the problem, but it's odd.

If I try to start the Thunderbolt Software application, I see an icon indicating that something is running, but there's no GUI and no way to interact.

- Jon

After you start the Thunderbolt software, all you get is a system tray icon, which you can then right-click to do a few things like view connected devices, manage approvals, and see some version information.  But I'd again recommend uninstalling and reinstalling the Thunderbolt software and then applying the appropriate Thunderbolt firmware update for your system.  And double-check you're on the latest system BIOS before you do any of that.