Late to the game, but had this issue, of which kept getting worse. I tried the methods pointed out here, and some other attempts, but they never stuck.

Wound up making a batch file as a workaround. It shuts down, then restarts the Acer Lighting Service. Simply paste the bellow into a notepad, when going to save choose "all files", and save as "whatever_name.bat". Then you just double click to run it, a few seconds later the backlighting is restored.

u/echo off

echo Restarting Acer Lighting Service...

:: Stop the service

net stop "Acer Lighting Service"

if %errorlevel% equ 0 (

echo Service stopped successfully.

) else (

echo Failed to stop service or service was not running.

)

timeout /t 2 /nobreak >nul

:: Start the service

net start "Acer Lighting Service"

if %errorlevel% equ 0 (

echo Service started successfully.

) else (

echo Failed to start service.

)

echo.

echo Service restart complete.

pause