Depth effect not working in my iPhone 7 plus

Take portraits with your iPhone camera

• With Camera  on models that support Portrait mode, you can apply a depth-of-field effect that keeps your subject—people, pets, objects, and more—sharp while creating a beautifully blurred foreground and background. You can also apply and adjust different lighting effects to your portraits.

There's a very good reason you can not get depth effect on your iPhone 7. It is NOT a model which has the hardware required for the feature to be supported.