Why isn't this GIF animating?
GIFs are awesome, but not all apps support them properly, which is pretty disappointing. Sometimes the image will accidentally be converted to a static image if you save it to Photos from apps that don't handle them just right, or when you post to a particular service from these apps.
To get around the issue when saving, you can add the GIF directly to your GIFwrapped library using the nifty "Save to GIFwrapped" extension.
If you really want to add it to Photos, GIFwrapped is pretty much guaranteed to save the image correctly. Be warned, though; Photos can't display your GIF as an animated image, and you won't be able to see it play.
Posting GIFs is a little trickier, but you can try copy and pasting to the app of your choice. Many apps support this because of the wealth of GIF keyboards available today. If all else fails, you can share a link to the GIF instead. It's not ideal, but it'll work.