Software update 14.6 and Apple accessories.

Can someone please explain to me why when I upgraded to IOS 24.6 on an iPhone 6s with an Apple smart battery case attached that post update, the phone didn’t recognise the case and it then fails to charge the handset properly?

Just to check the battery case, I connected it to an iPhone 7 still running IOS 14.1 and the OS recognised it perfectly, showing both batteries and their charge levels when the charging cable is connected.