Q: Apple wireless keyboard, caps lock light wont light

I have an older apple wireless keyboard (2009)

and recently the caps lock light has developed an issue

that being it never lights up, always stuck off.

caps lock does turn on and off so the button is working, but the light dont ever turn on.

I have tried changing the batteries and using multiple mac's to test it.

but have had no luck getting it to work again.

Any Ideas?