Thank you so much for using our theme SuperMag. If you complete all the steps as our documentation and still the image is not cropped then it may be due to the small size of image there. If the image size is less than the size defined in the Settings> Media then the image will not cropped. So please try by adding the image size greater than the size defined media. Example, add the image 1200 * 900 Px.
Featured image will only crop, no images added by the content is cropped.
Please try it once and let us know is the same problem remains.
We tested Acme Fix Images and it is working properly on number of websites and we are confident that this plugin is working properly.
1. Go to setting > Media and set the images size properly.
2. Go to appearance > Acme Fix Images and set the images size. Wait until all the images fixed.
And refresh your site.