Hi TM. I'm Greg, an Independent Advisor, Volunteer Moderator and 10 year Windows MVP here to help you.
Let's go over all the fixes for night light to see if one can get it working correctly, and if not make sure you have the best display driver installed since this is what governs it.
1) See fixes here working for night light:
http://m.majorgeeks.com/content/page/how_to_fix...
https://www.thewindowsclub.com/windows-10-night... (Avoid ad links which intrude into editorial copy, especially avoid Restoro ad)
https://www.tenforums.com/general-support/12523...
https://win10faq.com/windows-10-night-light-not...
https://www.youtube.com/watch?v=ga5mBe5uLrw
2) Update the Display driver from the PC or Display adapter maker's Support Downloads web page for your exact model number, HP Serial Number or Dell Service Tag - from the sticker on the PC.
While there check also for newer chipset, BIOS/UEFI firmware (very important), network, sound, USB3 and other drivers, comparing to the ones presently installed in Device Manager reached by right clicking the Start Menu.
if this doesn't give you the latest or ideal driver for what you need, compare it to the driver offered by the Intel driver update Utility here:
http://www.intel.com/content/www/us/en/support/...
or the Nvidia Update utility here:
http://www.nvidia.com/Download/Scan.aspx?lang=e...
or the AMD autodect utility here:
http://support.amd.com/us/gpudownload/windows/P...
For Display issues one fix that is working is to Roll back or Uninstall the Driver on the Display Device > Driver tab, restart PC to reinstall driver.
You can also try older drivers in Device Manager > Display device > Driver tab > Update Driver > Browse > Let Me Pick.
Then you will know you've tried everything in addition to Windows Update drivers.
3) Go over this checklist to make sure the install is set up correctly, optimized for best performance, and any needed repairs get done:
http://answers.microsoft.com/en-us/windows/wiki...
Start with Step 4 to turn off Startup freeloaders which can conflict and cause issues, then Step 7 to check for infection the most thorough way, then step 10 to check for damaged System Files, and also Step 16 to test a new Local Admin account. Then continue with the other steps to go over your install most thoroughly.
4) If nothing else helps you can run a Repair Install by installing the Media Creation Tool and choosing from it to Upgrade Now. This reinstalls Windows in about an hour while saving your files, apps and most settings, solves many problems while also bringing it up to the latest version 1903 which you need anyway and by the most stable method.
http://windows.microsoft.com/en-us/windows-10/m....
I hope this helps. Feel free to ask back any questions and keep me posted. If you'll wait to rate whether my post helped you, I will keep working with you until it's resolved.
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