10-03-2018 09:08 PM - edited 10-03-2018 09:10 PM
Using app on my iPhone 8 plus. Had same problem on my iPhone 6. I get the preview on what I'm going to shoot BUT.
Start recording and the picture goes away when hit start to record.
I just read that if using HEVC, live preview will not work during record. Go to the link and scroll down to limitations.
EDIT: My apologies...I just saw that you are using a HERO 3. HEVC would not apply in this case.