Problems rendering 4k project

Hi everyone,

I just edited a project with 4k clips (I normally work with 1080p footage) and had a lot of trouble with the rendering step. It finally completed the rendering process (~24 hours for a 30m video), but the .mp4 file will not open. I’m not sure what to do as I don’t want to lose the edit, but it doesn’t seem that I can process the project properly. Does anyone have any ideas?

Thank you in advance for all of your help.