GIFS are supported on Twitter, Google+ and Pinterest. They are not supported on Facebook or Instagram.
To fix that, export it to an online MP4 converter. If you plan on using it for Instagram, Instagram needs a minimum of a five (5) second video and Facebook requires 30 seconds.
When making your GIF remember that it's meant to be snack sized. It can be used for Twitter, Google+, Pinterest and even embed in your emails.