Whenever I plug my charger into my phone it says “this accessory may not be supported”

I have a real apple charger and cube basically the one that came with my phone but whenever i plug it into my phone it says “this accessory may not be supported” or something like that but it doesn’t make sense because it’s a real apple charger?? i plugged it into my sisters iPhone 7 and it didn’t have any problems for her

[Re-Titled by Moderator]