Cant get AR Camera to pick up target image

Hi

I have been using Vuforia and Unity for a couple months now. I have so far had no problem using the AR camera and target images, until I downloaded Android Studio and Vuforia Object Scanner (as I want to learn this).

Suddenly in all my projects the webcam no longer sees my target images!? (as in my models no longer appear above the many different target pages for my many different projects)

I have uninstalled Unity twice, the second time I also deleted everything on my computer I could find related to unity and android. No joy.

Has anyone encountered this problem before?

I'd appreciate any help as Im using this for my masters.

I have attached a screenshot (licence blanked out) of a very simple test project only using 5* target image, ar camera and a 3d cube.

My gut feeling is that there is something going on with a setting file elsewhere on my computer? Edit: Okay so just tested my models on my laptop and they all work on there. So its not a problem with my models.