After working on this issue with a Dell 7710 for some time here is what I figured out. If the WLAN is disabled in the BIOS, the Thunderbolt 3 will not work. Bluetooth and WWAN/GPS does not matter. If the WLAN is disabled, you won't ever get Thunderbolt to show up. Dell should know about this now because of me working with them.
We normally turn WLAN (WiFi) off in the BIOS at our facility. But I never thought WLAN and Thunderbolt would be somehow connected. Here is how I figured it out. We had an HP laptop from another group that needed reimaging to Windows 10. I noticed it had Thunderbolt 2 which is the mini Display Port connector. So I thought... hey, I could see if my Sonnet ExpressCard to Thunderbolt device might work with it. And it did! So I took screen shots of it and of the Dell 7710, mostly of the device manager by connection display stuff. That excited Dell enough that they wanted to replaced the motherboard. So a tech came out with new motherboard and I/O board. I watched the replacement process and noticed a module. I inquired and the tech said it was the WiFi module. I said that it was bought without WiFi. Of course he said it's there anyway. That just stuck out in my mind.
Okay so the boards were replaced and I tested... Thunderbolt 3 worked! How can that be? So I have two of these laptops that were bought together so I started comparing everything methodically. And the final determination was that if WLAN is turned off in the BIOS, then Thunderbolt 3 will not do anything, won't show up, no nothing as if it doesn't exist. Turn WLAN ON in the BIOS, Thunderbolt 3 works beautifully! BIOS versions did not matter.
So my Sonnet ExpressCard to Thunderbolt Adapter connected to a StarTech Thunderbolt to Thunderbolt 3 Adapter connected to the Thunderbolt 3 port on the Dell Precision 7710 using a StarTech Thunderbolt 3 cable works very well. Perhaps in a future BIOS update Dell will fix this issue but I don't know. The latest BIOS 1.10.7 was released Mar 9, 2017 but looking at the fixes I'm not sure this issue would have been fixed. I would have to try it out and see. Hope this helps someone out there.
I told Dell all about this as it is somewhat important. In a secure facility, they want you to demonstrate the WiFi (WLAN) is turned off in the BIOS. Otherwise I have to Disable it in Device Manager and I don't know if that is acceptable yet. Disabling WiFi in Device Manager allows the Thunderbolt 3 to still work.
