^This, exceeding the dimensions 250x80 is what prevents animation.
If you go to upload new files, you get a warning about the file size limits, but not the pixel size limits.
Annoyingly, you can still upload images of larger dimensions, but as you found out, they won't animate until you click on them.
I found that out the hard way too, after spending a lot of time making custom promos for my friend's OF, Fansly and others.
Good news, plenty of freeware editors out there that work well and let you resize your gifs.