So I created a new project and added an ARCamera. This imported Vuforia scripts. Then I copied the files from that new project replacing the ones in the old project. This worked.

Well, this isn't a solution but it's a workaround. Search for calls to "VuforiaRuntime_RegisterVuforiaInitErrorCallback" in XCode and comment out calls that aren't explicitly made by your code. Then you can handle the errors on your own. I'm guessing this is an issue arising from me sloppily porting over from the old Vuforia to the built in Vuforia, so probably an error on my part, for some reason it's impossible to remove the default vuforia DefaultInitializationErrorHandler.

Really stuck here. It seems that registering a new callback is fine, but there's no way to edit or unregister the green screen view.

Hey does anyone at Vuforia have any idea how to change the default green and white error screen when camera access isn't granted?