External monitor not working with thunderbolt connector

[Dan8719]

Dear all,

in past months I had a problem with my laptop: HP Spectre x360 Laptop - 15-eb0017nl ( it has 2 thunderbolt ports with type C connector and 1 HDMI connector. Moreover there are 2 graphics cards: an Intel one decidated to the laptop monitor and a Nvidia GeForce for the external monitor). The problem was the following:
when I tried to connect the laptop with the external monitor there was no way to make it working. I tried to connect the external monitor in the following ways (and with different monitors):
- with thunderbolt (usb-c connector) to DisplayPort directly to the monitor

- with thunderbolt (usb-c connector) to HDMI directly to the monitor

- with thunderbolt (usb-c connector) to VGA directly to the monitor

- with DisplayPort to DisplayPort cable connected to the HP Thunderbolt Docking station 120W (6HP48AA) 

- with HDMI to HDMI cable connected to the HP Thunderbolt Docking station 120W (6HP48AA) 

without any success.
The ONLY way to make the external monitor working was to connect it directly through the HDMI connector of the laptop.

After several attempts with the HP support trying to update several drivers (related to everything) and reinstall also the Operating System the HP service (after almost 10 iterations and 2 months)  gave me the solution which I want to share with you.

You need to go to the device manager, then Graphic cards, and choose the one related to the external monitor (in my case the NVIDIA one). Right click, properties, details, GUID class, and take note of the code.

Now enter the REGEDIT and enter the following directory: \HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\

finally choose the folder with the same name of the code you took note befeore, then choose folder 0002 and set the RMEnablePhyRepeater entry to 1 (in my case it was set to 0). Shut down the laptop and switch it on.

This finally fixed the problem.

[Mauro71]

I had posted the same problem yesterday.

I used the same procedure indicated by you and finally I solved.

The onslu difference is that in my regedit configuration I don't have the folder 0002. The indicated key is in 0000. Do you have any idea about this difference?

I changed this parameter and magically the second screen was displayed.

Thank you very much.

Mauro

[Dan8719]

Dear Mauro71,

actually I have no idea about the meaning of 0000 or 0002 folders and so on, but I'm happy to hear that my post has been useful for someone since I wasted a huge amount of time with HP Support in trying to fix that problem! 

[Petertherockuk]

So sad. I don't have the file RMEnablePhyRepeater. 

I am having the same problem as everyone. New Dell monitor purchased however no signal in the usb c on the monitor from the hp spectre laptop, the laptop is charging though.

[Jonas_81]

Thank you so much for posting this information! This problem was driving me completely mad, and your solution solved it.

( I registered on HP now just to say thanks to you )

[Jonas_81]

I did not have the entry RMEnablePhyRepeater either. I added it (DWORD) and set it to 1.

I had no high hopes doing this - but the screen turned on 🙂

The "Device was not migrated due to partial or ambiguous match" and black screen was driving me crazy.

( I did another thing, that perhaps was needed, perhaps not - I started the Thunderbolt Software and enabled the Screen there, before I tried this. But that only enabled all the USB jacks)

This was on a (Spectre x360, thunderbolt 3 port), connected to a an LG UltraFine 5k screen (Bought to work with my Mac).