I have exactly the same issue with a different TB16 dock. Would love an answer but none of the similar threads help. I've tried disconnecting the battery and resetting the dock. Also all firmware are up to date. Anyone out there with an answer?

I have a 5540 and the same issue.

Dell wants to replace my regular charging port, under accidental damage??

Dell Support are totally ignoring the fact that it is my docking station port that is having troubles.  

I replaced my laptop battery yesterday. Thought that may be the problem since it was two years old. That did not fix the problem.

Basically the TB16 dock no longer charges my laptop at all.

I have this problem.  Dell Precision 5540 with TB16 dock.  The battery doesn't charge at all when the docking station is connected to the USB-C Thunderbolt port regardless of whether I connect it first or last with the AC adapter supply.  Any resolution for this issue?

The Dell Docking Station WD15 is a device that links all your electronic devices to your computer using a USB Type-C cable interface. Connecting the computer to the docking station enables you to access all peripherals (mouse, keyboard, stereo speakers, external hard drive, and large-screen displays) without having to plug each device into the computer.

* Read through this, "How to Use and Troubleshoot the TB16"
* Read through the "Driver Installation Guide for Dell Thunderbolt Dock TB16"
* TB16 firmware update procedure
* Read through the Dell Commercial Docking Compatibility which details what AC adapter is required for PC and docks

Has anyone managed to fix this?  I have had exactly the same where the dock no longer charges but will show external displays and USB devices on the dock can be used.  It used ot be as long as you plug the AC adapter into the Laptop first and then the thrunderbolt dock it could be powered.

This has now matured into an issue where the laptop no longer charges with the AC adapter connected only.  I cna sometimes get the laptop to charge if the battery is completely dead, I plug int he AC adapter and then boot up.  Once into windows I then plug in the thunderbolt dock and sometimes that will get the battery charging.

So far I have tried different Dell AC adapters, replaced the DC jack in the laptop and have also replaced the battery. I just get the ac adapter warning message on boot up every time.  All the diagnostics suggest everything is fine apart from the AC adapter being unknown.

Most frustrating.

I have exactly this same issue with a Precision 5530 and a WD15 dock.

This is a business setup so my first port of call was to my internal IT team. They immediately sent me a replacement WD19 dock which made no difference. I was advice to ensure that I had all the BIOS, Firmware and device drivers up-to-date - which I did but made no difference. They then sent me a replacement Precision 5530 after Dell warranty support advised that they wanted to change the motherboard. Replacement laptop in place and seemed to resolve the issue - the laptop charged and remained charged whilst connected to the dock only. However, this was short lived as only 3 days later the laptop advised me that the battery was critically low and I needed to attached it to a external power source!!! I tried all the troubleshooting that I had on the previous laptop - BIOS update, Firmware update for the dock and the TB port, Driver updates.. all to no avail. My next step is to drive 50 miles into the office to show the IT team the issue. 

Frustrating and disappointing !

Given that there is no confirmed solutions from impacted users that took the time to raise this issue and post it here, has Dell support has been able to recreate and solve it in a lab? It is possible that one of the impacted users may not have followed firmware update procedures properly and was unable to solve the issue but unlikely that all of us here don't know how to follow firmware update steps. There are probably many more in the field experiencing this problem and frustrated with Dell quality. It would be good for Dell Precision user community to have a definitive answer from Dell - declare it as a defect with no fix so we don't keep wasting time trying to fix it. I think everyone will appreciate some transparency here.

Thanks

so this just happened to me this weekend.  Dell Precision 5540, and the WD19TB docking station.  It worked fine for the last 2 months that I had the dock, and now won't power the laptop via the dock.  Yet I also have a 5530, and it works perfectly fine.  The 5540 had a firmware update last week, but ran fine for 3 days after that before this issue happened. I'm hoping it is a firmware issue and a future update will fix it.