Trouble with video

I am having issues with video. I open sessions that worked yesterday and they do not recognize the video today. The video track is a gray block and there is no picture at all.
I restart my computers and some of it comes back and some of it doesn’t.
I am using 8.0.15 and I do have the dnxhd plugin working.
I also have trouble importing video and am having to convert to H264 for it to work which does not look as good but it keeps me working.