September 12, 2014, 04:17:56 am
MP4 files are difficult to repair if they do not complete properly.
Which version of Lumion were you using to render for 52 hours? Whew
, that's a long time
If WinFF can open it, it might be able to re-save it, otherwise you might need to consider rendering each of the clips, or render all as Images.
What sort of PC are you using and how heavy was the scene? Did you use lots of Reflection Effects?
Do you know the reason why the PC shut down?