PlaneFinder doesn't show up in certain situation

Hi, We use iPhone 12 to try out an empty project with the ground plane feature (using unity 2019.3.1 & Vuforia ver.9.4.6) and everything works fine. However if we use the ground plane in our current work project, the plane finder just doesn't show up most of the time for iPhone12 and strangely it works in Sony Xperia phone without fails. In our project, there will be a few levels being loaded using additive scene loading method. The initial scene will not have AR cam as well as any other AR component, instead the second additive level will implement these AR features. We wonder whether or not is this loading scene method causing the problem. Also is there any way that can re-initiate the plane finder behaviour. We have tried re-enabling the ground plane and the plane finder's components, but it still won't solve the problem. We have tried several ways and still have no clue. Any help would be much appreciated!