Not fixing the problem

I click on PTE in edit image in media library. It allows me to crop when I select PTE thumbnail. When I say ‘save’ it opens another window with my thumbnails displayed as ‘large’ ‘medium’ etc I click on the size I think I want it to be and that’s it. Nothing else happens. There’s nowhere to save my selection – no point to it … I go and look at site and nothing has changed. Switched off Easy Columns plugin. No difference.
What I want is for the thumbnail to be a smaller version of the original image – and not cropped so that parts of the image are missing.

Thank you so much if you can help me (or if you can’t) must be something with my site. I have built a very basic and simple site using twenty twelve as my theme – with a child theme for my changes. The child theme is on display – only way I can get rid of ‘Proudly powered” in the footer.

https://www.ads-software.com/plugins/post-thumbnail-editor/