The movie I am trying to play was originally downloaded to the Videos folder on my Surface Pro and I moved it to my SD card. When I had the movie in the Videos folder and played it on the Windows 8.1 Xbox Video app, it worked fine. When I moved it to the SD card and tried to play it through the Windows 8.1 Xbox Video app, it gave me an error; however, when I still had it in the SD card and played it through Windows Media Player, it worked fine.
From what happened, I'm thinking its an owner file property/DRM issue, because the owner file property changed from my username to "Everyone" after the file was moved to my SD card. Since the WP 8.1 Xbox Video app can download videos to play offline, I'm assuming it also downloads them as a WMV file like the Windows app. So I don't know if playing the video through moliplayer would change anything because Xbox Video also supports the WMV file type.