Spectre x360-15-bl012dx External Monitor Not Working in WIndows 10

[MarkWNY]

Laptop Computer Spectre x360-15-bl012dx running dual boot, Windows 10 64-bit and Ubuntu 18.04 Linux.  About 1 year ago, my laptop screen was getting very "flaky", especially as it warmed up or if the brightness was not at max.  By "flaky", I mean that it would lose sync and start displaying shaky or double images.  It worked fine if I used an external monitor.  At that time, it was only running Windows 10 (not Linux).  I found online that other people were having similar problems with their displays, so I purchased an external display and a second (other brand) computer as a backup.  After I migrated my work to the backup computer, I decided to put Linux on the HP in a dual boot configuration.  I used Linux almost exclusively for almost a year, only booting windows occasionally.  Somewhere along the line I found that the external monitor stopped working in Windows, but worked fine in Linux.  The monitor is a Dell S2319NX.  Several firmware/software updates occurred over this period under Linux and Windows.  I believe one of the updates under Linux may have been incompatible with Windows, but that's just a guess.

When I go into Windows Settings/System/Display with the HDMI cable attached, there is one display shown with a 1|2 in the Rearrange Displays section.  If I click the detect button, it says "Didn't detect another display".  The Dell monitor says "No HDMI signal from your device".  If I disconnect the HDMI cable, the Rearrange Displays section goes away.  

I've used HP Support Assistant to make sure everything was up-to-date.  It updated BIOS, but that didn't help.  Any other ideas would be appreciated.

[Riddle_Decipher]

@MarkWNY HP does not recommend or support use of Linux or a dual boot on the device, that said, considering the issue occurred on Windows long before you got Linux in there, this could be an issue with the monitor drivers, to be sure, perhaps, you could connect an alternate monitor or a TV to your laptop and check if that works fine.

Also, try another cable (If available) and let me know how that goes.

P.S: Welcome to HP Community 😉

If you wish to thank me for my efforts, you could click on "Accept as solution" on my post as the solution should help others too.

[MarkWNY]

Sorry for the delay.  I finally was able to try another monitor and new HDMI cable.  Symptoms are the same.  It works fine in Linux, but not Windows.  I acknowledge that HP doesn't support Linux or dual boot.  At this point, I suspect there is an incompatibility between the two OS's as far as the treatment an external monitor.  For example, I seem to remember that the firmware updates occurred sometime ago under Linux.  Perhaps the laptop firmware has been changed under Linux that is incompatible with Windows.  Just a guess.  Anyway, I understand if I wish to use Linux on the machine, that this is unsupported and I'm at my own risk.

Thanks for the help,

Mark

[Riddle_Decipher · Accepted solution]

@MarkWNY As mentioned earlier, HP doesn't support nor recommend using the Linux OS, I suggest you look for the most recent firmware/Bios update and install the same, then check if the issue is resolved, after restarting the pc in windows, without the Linux on dual boot, etc..

If you wish to thank me for my efforts, you could click on "Accept as solution" on my post as the solution should help others too.