External monitor connected via USB-C/Thunderbolt 3 has no signal

@TheProgrammer2  I can think of two possibilities here.

The first is that this may be related to the issue described here. I know the article only mentions the XPS 13 9350, but after it was published, multiple users confirmed the exact same behavior on the XPS 15 9550 and its sister system the Precision 5510. Dell frustratingly never went back and updated that article. But as you can see, it describes an issue whereby that system won’t output video over USB-C even to Dell’s own USB-C displays. That includes USB-C displays created long after that article was published, so it appears to be something on the system side. Dell never explained the underlying cause of this problem, never mind offering a fix (other than “Buy one of our docks”....), so it’s tough to say for sure, but if you’ve confirmed that everything works as expected with other systems and have already updated drivers (and the BIOS?), this is the likely culprit.

That said, multiple users affected by the issue described in that article also found that at least some USB-C to DP and USB-C to HDMI cables worked fine, and the fact that Dell’s own docks work with the affected systems, including their USB-C dock that relies on exactly the same technology that your adapter would be using, indicates that there are at least some products out there that would work. Which leads me to the second possibility.

Even with systems not included in the scope of that article I linked, I’ve now seen at least 5 cases on this forum where reported that USB-C to HDMI adapters/cables worked with some systems and not others, and in all of those cases, the solution was just to get a different brand of cable/adapter, which ended up working with all of them. Obviously that shouldn’t have been necessary, but the reason I recommended it is that USB-C ports natively provide video output using DisplayPort, and therefore USB-C to HDMI cables/adapters need to incorporate an active signal converter chip to switch that signal over to HDMI. That adds complexity, and it seems that complexity can create interoperability issues that only arise with specific pairings of devices. The fact that your adapter supports up to 3 displays means it incorporates an MST hub, which adds another element of complexity compared to more typical adapters that only support one external display.  So if possible, you might want to just try another brand of multi-purpose adapter. 

Thank you a lot for your detailed answer!

First of all, yes I also updated the bios. I also tried various settings of the bios with the Dell Docking station via USB-C enabled/disabled as well as the security mode of the ports on the dock to set to 'no security'. Nothing helped. 

Would you say the problem is mainly the HDMI port or would the displayPort port also be a problem? I unfortunately have no displayPort cable at home and hence cannot test it.

But you also said the Dell Docking station is working for sure? To be honest it is not only the price of the docking station but also the less ports and I do not like the design of those plastic casings, they don't look that premium.. 

When I try another adapter from another brand do you have anything I have to consider to know whether or not it will work? Do you know some that would work? 

Thank you!

One thing I did not mention so far: The user manual says that the adapter might need an additional power supply since it consumes 8W itself. Is the additional power supply only needed if I want to charge my notebook via the adapter or might this cause the issue with HDMI since the signal converter chip you mentioned needs more power? 

Otherwise I would just buy the dell docking station and hope I do not have any more problems. 

@TheProgrammer2  Whether the device needs an external power source depends on how much power the laptop provides over its USB-C port. And sometimes an adapter can work both unpowered and powered and will work BETTER powered. For example, sometimes adapters like that when connected to an external power source will provide more power out of their USB ports to better support high power draw devices like USB-powered hard drives, which would not otherwise work properly through the adapter when the adapter is relying on system power to run both itself and whatever else you attach to it. There just isn’t enough power available in that type of scenario. However, I’d be surprised if that adapter when paired with the XPS 15 couldn’t run the HDMI output though. HDMI only even offers a tiny amount of power out of its port, so if that adapter couldn’t even run that output when unpowered, I would think it would be mostly useless. The Anker adapter I have is able to run an HDMI display even when the adapter itself isn’t connected to power, for what it’s worth.

A client bought a Dell XPS 13 9365 from a clearance company. Cheap but the first thing I always do is take an image using Macrium Reflect Free. I couldn't get my (working) Anker USB-C docking station to work - wouldn't recognise any USB devices (2.0 or 3.0) plugged in. In fact, it didn't appear to be showing up correctly at all in UsbTreeView (great utility, recommended). 

No amount of driver updates could fix it. I then came across this article:

A Closer Look at USB-C Problems on Some Dell XPS and Precision Laptops - Plugable Knowledge Base

Which sounds spot on - hardware design problem causing interference between Wi-Fi antenna and USB-C circuit. More hits home that this is the second attempt - first one went back because Wi-Fi signal was useless. One of the "fixes" is to reduce Wi-Fi strength.