Screen brightness control lost after updating Windows 10 from ver. 1909 to 2004

[FGomez]

After updating Windows 10 from ver. 1909 to 2004 the computer lost all capabilities to control the screen brightness, including the HP built in F2 and F3 functions. Even though the Mobility Center displays a brightness control bar (the only place where it appears), adjustments do nothing. Additionally, the blue light settings for night light are completely inoperative. I believe creating a new driver and/or an update for the BIOS would be necessary.

FG Jun-14-20

[Echo_Lake]

@FGomez

Thank you for posting on HP Support Community.

Don't worry as I'll be glad to help, I have a few troubleshooting steps we could try to fix the issue:  

Firstly, perform Windows Update and HP Support Assistant: (do not skip any troubleshooting steps if you feel steps are repeating) 

To check for updates now, select the Start button, and then go to Settings  > Update & security  > Windows Update, and select Check for updates.

Install updates from HP Support Assistant: Go to Download HP Support Assistant to install the tool.

1. To open HP Support Assistant, double-click the HP Support Assistant icon .
2. Click My devices in the top menu, and then click Updates in the My PC or My notebook pane.
3. Click Check for updates and messages to scan for new updates.
4. Review the list of updates. Updates with a yellow information icon are recommended. Updates with a blue information icon are optional.
5. Click the update name for a description, version number, and file size.
6. Select the box next to any updates you want to install, and then click Download and install.

And, also run BIOS Update: Follow steps from the link: https://support.hp.com/in-en/document/c00042629

Hope this helps! Keep me posted for further assistance.
Please click “Accept as Solution” if you feel my post solved your issue, it will help others find the solution.

[FGomez]

Thanks for your input. 

All steps were already made, BIOS = F.50 (Latest available) , All diagnostics passed (including all keys in keyboard check ok), Windows update reports "Up to date" as of today (Jun-17/2020), SFC reports files NOT corrupted

I see many other users having the same problem. It must be a big bug in Windows!

I'm going to start Windows in "command prompt" mode to see if the F2 & F3 keys actually work before the operating system is loaded.

Questions:

1) Besides performing a factory restore, is there a manual verification (maybe inspecting the registry or prompt command) to identify the proper configuration assignations of the function keys?

2) Is there an HP application that can be used/downloaded to reassign function keys?

3) Have the other users been able to recover brightness and blue-light control?

4) Where can I find the ISO image of the 2004 version of Windows to attempt re-installation?

Cordially,

FG-Jun-17/2020

[Echo_Lake]

@FGomez

Thank you for posting back.

Two OS recovery option are available:

• Local reinstall : Using OS files on local hard drive to re-install Windows. When there is no Internet connection, this is the default option in PBR recovery process.

If you initiate a PBR with Cloud Download it will get the “latest” released Windows image files from Microsoft instead of using existing Windows files.

[FGomez · Accepted solution]

Ok. However, I found that the installation of update 2004 was faulty, causing the MONITOR device to load a LOCKED copy of the Generic PnP Monitor. For which I deleted the device and re-initiated the computer. Additionally, I added the DWORD  variable "FeatureTestControl " = 0000ffff

to the Registry in HK_LOCAL_MACHINE key:
System\ControlSet001\Click Control\Class{4d36e968-e325-11ce-bfc1-08002be10318}\000
This procedure restored the F2 and F3 Brightness Control.

However, some other problems persist. Please indicate where to access the 2004 update to attempt reinstall, since Windows "believes" the the update is installed and does not show in the list of new updates.

Sincerely, F.Gomez - Jun-19-2020