Exports as file instead of mp4

I have a video that I edited in shotcut - when I go to export my video as an mp4 it works, but then when I go to open the video that it exported it just is a file, and it does not open. I just exported another video the same way as I did this one as an mp4 and it works perfectly. HELP

Sometimes you need to make sure you add .mp4 to the file name when you export/encode.