unable to focus close objects after replace camera lens

Two things typically happen in this scenario, either the camera's shorting out and disabling itself before the camera comes in the focus leaving the app in and unfocused state; or it's not's aligned with the camera hole on the phone. It maybe constantly trying to focus on the piece of perimeter in front of it making for a permanently unfocused state.

The purpose of that transparent bracket is the hold everything in place. Even a millimeter often wreck everything.

Cameras often come with brackets when you purchase them, and the bracket alone can be as much the camera even. It might be worth getting a new camera lens bracket combination.