Images won’t post large size

I want the images to show up big like it did the first time I posted. I can’t re-create it. The size of my featured image was wrong so I changed it to a square and re-uploaded and re-shared. Now it is putting the image inside a small rectangle link box. I do not want that. I want it to look like the TRIA post below it. I have changes the settings from simple to advanced several times and changed the size of the photo and can’t get it to post with a large image below the excerpt. Please help, new to linked in.
Thanks!

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