Q: Help turning keyboard backlight off?

Already tried that, brightness has stayed the same, can't turn it off or adjust it in any way. Could it be my bluetooth keyboard? It's Apple but it's a few years old, so maybe F5 won't turn down the backlight. I don't know.

It half-helped. The backlight now turns off when I'm not using my computer, so it won't bug me while I'm trying to sleep. I still have no way to keep it off while I'm using it but it solves my biggest problem. Thank you for your help.