GoPro - Video wont play.

I have loaded video from GoPro onto MAC and IPad and now they wont play. It has error saying "operation not complete" and MP4 on video screen?

The original video's played this time last year and I was able to load and play video's, but all video since then and all old video's wont play and the video has been replaced with a grey box saying MP4.

This happens on both IPad and MAC laptop.

Can anyone help?