You need to use the picture url itself with the file extension at the end, not the link to the Imgur page it is displayed on:
[IMG]https://i.imgur.com/YdlCNIv.png[/IMG]
That should be the code you're using. It gets you the below:
What you were using before was this:
[IMG]https://m.imgur.com/YdlCNIv[/IMG]
Notice how there's no file extension at the end of the URL? It's because that's the link to the Imgur page the picture is displayed on, not the picture itself. You can get the link to the picture itself by clicking on the picture on that page, though.