Single Blog post image size will not resize

Hi Team,
Sorry to write in again on this one.
Can not seem to figure out why my featured image single blog post is being cropped.
Original picture size is 600×600
I want the theme to expand it to content width and keep height same aspect ratio (1:1)

I have tried the regen thumbnails plugin at least a dozen times.
I have also tried to change the child theme functions.php but it seems to have no effect even after I regen thumbnails.
I have also tried the simple image resize plugin. tried to set to “no crop”. Still no luck
Tried to clear browser cache. What am I missing here? I can see the theme is still determined to put in a 600 x 423 image.
Here is the link: http://victoriamaxwell.com/wp2/depression-no-laughing-matter/

Login details sent in private
really hoping you can figure this out, I need to move on.

Thanks, Steve