It may be a problem with your browser or lemmy-ui, you could try with a different browser and/or open an issue on the lemmy-ui github repo.

Some instances are under a fairly heavy load at the moment, gifs are fairly big files, so it could be that.

If you try to download the gif directly (copy/paste the url into the browser’s url bar) it will probably return 502 Bad Gateway if that’s the case.

Also new to Lemmy, but it looks like it only really matters which instance you register with if the instance shuts down (your account will be lost).

You should also try to pick a smaller instance, to avoid unneccessary load on the few ‘main’ ones, but also make sure you’re on a reliable instance, since you’ll lose access to Lemmy in downtime.

Also, when communicating with other instances, they can see the one you signed up to (I’m on sh.itjust.works).