Keyboard backlight does not light, even after replacement.

I bought a used MBP, Early 2008 Macbook Pro 15". A1226, that came with a French keyboard, and the backlight was intermittent. I replaced the KB with a US one, and that works fine, except for the backlight.

When I use the F5/F6 keys, the [on-screen backlight] indicator moves, but no change in the light. In System Preferences I have tried automatic and manual control for the backlight - no change.

Nothing is blocking either the speaker grille or the webcam area.

Ideas?