How are you posting gifs???
This process usually works:
I go to duckduckgo, and type in something like "camping gif", click on "images". You'll end up at a URL like this:
camping gif at DuckDuckGo
Click on an image that you want. Then long press (or right click) on "view file". Select "copy link address".
(Exact wording may vary with your browser.)
Then back on the CF page, when you're composing a message, click the little image icon. It's right above where you enter the text. Next to the smiley face.
A box will pop up where you enter the URL that was saved to the previous step when you copied the link address.
(The URL has to end in png, jpg, jpeg, jpe, gif, or svg. An animated gif will end in gif.)
Paste the gif URL into the box. Then click "insert".
You're welcome to test it out in this thread!