I backed up a video clip through my Flux device and it will not play on my PC.

Typically this is one of two things.

1) Make sure you are using the VLC Player.  This is a free to download player you can find here.  Many other players will require certain codecs that some PC/Laptops may not have.

2) You downloaded your clip as private format instead of AVI.  It is recommended to download using AVI to avoid issue.