AR model not anchoring - Sketchup mobile viewer

Having limited success anchoring a sketchup model in AR on the mobile viewer. I have a samsung S8 and have had the AR function working before. Now when I try to anchor and it says to tap on the mesh, it simply won’t anchor. I noticed the finger icon is black, not white as previously seen when it had worked. I have reduced the sketchup file size (around 6mb) and reinstalled the app but having no luck. Feel a bit jipped paying for the AR functionality and not able to use it. Any advice?