After spending ages trying to find out what was wrong with loading my videos and why it was giving me a sandbox error warning, I found out that I was missing the line:
After adding this line the warning went away. It did come back up once when I tried it but then the video played anyway. Ken had advised to download the videos and put them into the program but I feel that unfortunately I don’t have the time to do this. I do know in future to always download and put the videos in that way.