If the cover does not charge other pen, the keyboard cover is broken. It is common failure when using the keyboard counterside flipped.
If other keyboard cover is functioning alright for your surface, the device is okay. Only the keyboard cover is defunctioning i guess.
I'm not sure if the support department will accept the replacement or not, but you can ask them to accept.
I am sorry that i don't have any problem with newer firmware on my surface 8 or 9, maybe the defunctioning unit is the keyboard not the firmware.