It’s strange, I downloaded a gif to my photo and selected it as an image for a Memmy post. The post worked and was upvoted so others must see it. But the actual gif is not visible on Memmy. The gif does play on a mobile browser though.
I want to try posting a direct link to a gif and see what it looks like. Can you see the gif below?

It looks like you need to use the format:

such as: 














It must be a limitation of Memmy then. Or at least I don’t know how others are getting it to work. Sorry I don’t know. The gif plays on my mobile browser just fine but just shows a box on Memmy.