Iphone Xs Smart Charging Case Not Working

I have purchased three separate Apple brand Smartcharging cases for my iphone Xs.

The case charges fine when plugged in on its own/ the light on the case turns green. When I insert and connect it to the phone, the phone recognizes the case as being present. However the phone shows the case as having 0% charge, and does not start charging the phone. When I plug in the case with the phone inserted, the phone starts charging, but not the case. So in other words although the phone recognizes the case as being present, it will not charge the phone.

As I said we have returned two separate cases, so I think the issue is with the phone.

Any help would be appreciated.