Error when exporting video

Hi there, 

I'm exporting a video i've created on rush and it exports no problem but then when I go to open the file it says this: 

" This file isn’t playable. That might be because the file type is unsupported, the file extension is incorrect, or the file is corrupt. 

0xc10100be "

I've exported it 7 times, 2 of the times it has worked but I need to make changes. It's 30 minuties but I have done longer videos before this. I'm just not sure what is going on and I need help please!