Bought a 7470 refurbished through Amazon. All good except there's no backlight. The keyboard has the illumination key on F10. Fn is functional on all other F keys.

The connectors:

I checked the connections, purged CMOS by removing the battery etc. The BIOS:

<To protect you, your private information was removed from public view. All private data was saved to your private Case. DELL-Admin>

From what I've read, there's no solution and I don't know whether this is a hardware/firmware/software issue. The only abnormal thing I noticed is that the service tag in the BIOS is different than the one on the back of the case. I tried to use different versions of the BIOS, back to 2016, with same result.

I'm thinking about replacing the keyboard, unless someone has some genius insight. Thanks!