Macbook Pro backlight not working correctly

I have the MacBook Pro (15-inch, 2018) with Touch Bar, and it works well except for the keyboard. It's supposed to light up, which it always did until a year ago, then it just stopped.

At the time I did the following:

Adjusting the backlight brightness

Change Keyboard preferences on Mac

Updated Macbook to latest software

Using safe mode to isolate issues

Resetting SMC

Nothing helped so I made an appointment at the local apple store, and they ran some diagnostics, and they ended up sending it back to have the entire keyboard and Touch Bar replaced (and all other hardware connected).

After I got it back, it all worked again perfectly, until recently. The keyboard lights up just fine when starting the computer, but then turns off once logged in. So it's not a hardware issue.

Since then I've tried the following:

Adjusting the backlight brightness

Change Keyboard preferences on Mac

Updated Macbook to latest software (11.3.1)

Using safe mode to isolate issues

Resetting SMC

Resetting my MacBook Pro and reinstalling Mac OS

Nothing works and I am at a loss... my only theory is that this particular version of Mac OS thinks this MacBook Pro is actually an iMac or Mac Pro, because I don't see the keyboard lighting settings in the System Preferences>Keyboard menu...

Thanks for any help!