Additional chat-related features and issues within Microsoft Teams for business
Hi Sarah, I hope you're doing well, sorry to hear you're still having issues with getting GIFs to appear on Teams.
I'm not sure if the issue is specific to your Microsoft account or your Teams installation, so I think that would be a good place to start. Could you try opening the web version of Teams which can be found here and see if GIFs work there for you?
Kind regards, nt1809