T440p keyboard backlight issue

I have a T440p which came with a non backlit keyboard, which I wanted to replace it with a backlit one. After installing the new keyboard the backlight wouldn't come on (Fn + spacebar, the keyboard has the light icon on the spacebar). I tried swapping it out with a friend's keyboard (from a t450s which was replaced due to a damaged key) but without any luck.

Could this be an issue with the motherboard or controller? What are my options?

Thanks!