Q: Keyboard won't light after installing Digital Camera RAW Compatibility Update 6.19

Hi goosesq,

Hmmm, you installed Digital Camera RAW Compatibility Update 6.19 and now the backlighting on your keyboard doesn't work.

I gather you are testing in the dark or with the ambient light sensor covered up?

Portables: Adjusting the keyboard backlight - Apple Support

While in the default mode, the F5 and F6 keys will function only while the light levels are low enough for the ALS to trigger the backlight keyboard. By covering the ALS, you can test the backlight keyboard feature and adjust it with the F5 and F6 keys.

If that's not it, since it seems like a software change triggered this issue, let's try isolating software issues.

Please see if a Safe Boot allows the keyboard to light up.  That loads a minimum system to help isolate software issues.

Try safe mode if your Mac doesn't finish starting up - Apple Support

What is safe mode?

Safe mode (sometimes called safe boot) is a way to start up your Mac so that it performs certain checks, and prevents some software from automatically loading or opening. Starting your Mac in safe mode does the following:

• Verifies your startup disk, and attempts to repair directory issues if needed
• Loads only required kernel extensions
• Prevents Startup Items and Login Items from opening automatically
• Disables user-installed fonts 
• Deletes font caches, Kernel cache and other system cache files

Together, these changes can help resolve or isolate issues related to your startup disk. 

Starting up in safe mode

Follow these steps to start up into safe mode.

1. Start or restart your Mac. 
2. Immediately after you hear the startup sound, press and hold the Shift key.
3. Release the Shift key when you see the Apple logo appear on the screen.

After the Apple logo appears, it might take longer than usual to reach the login screen or your desktop. This is because your Mac performs a directory check of your startup disk as part of safe mode.

To leave safe mode, restart your computer without pressing any keys during startup.

If that doesn't help, see if it's an issue with your user setup by testing with another user.

How to test an issue in another user account on your Mac - Apple Support

Please let us know how that goes.