Are they the exact same movies that work from the tablets on memory?
Some files have different audio formats that do not work on all players(AC3 audio used to cause all kinds of problems with no audio. converting it to mpeg audio always fixed it).
What model of tablet is it? Does it run windows by any chance? If it does you can try VLC it play anything.
Seems you can get VLC for android too https://play.google.com/store/apps/details?id=org.videolan.vlc.betav7neon