I dont know why it says invalid image, but here is the imgur link: https://imgur.com/a/ZunCS
Because you used the link to the page rather than the link to the image. You need to right click on the image and "Copy image address"
Code:
Wrong
[img]https://imgur.com/a/ZunCS[/img]
Right
[img]https://i.imgur.com/G1zMZxk.png[/img]
[img]https://imgur.com/a/ZunCS[/img]
Right
[img]https://i.imgur.com/G1zMZxk.png[/img]
Like this:
