But it seems this only works when the player is on the right and bottom relative to the camera target object. It doesn't work otherwise.
Does zoom work? Or both camera movement and zoom are not working?
Try enabling "unbounded scrolling" in layout properties. Also check parallax setting on layers.
By the way, instead of lerping you can use MoveTo behavior to smoothly move the camera with nice acceleration and deceleration effect. And Tween behavior (value) to zoom in/out.