Thumbnails not resizing

Hi
I have Solidres free version which came with a template I bought. I changed the thumbnail size as the pics were looking awful, lining up down the page. Now, even though I have regenerated many times - images do not display on front end unless you click on image link, when they do open in a lightbox. Please see attached.
Any help appreciated.
Thanks

Sorry- should have said they have resized but are not displaying.