Dashboard thumnail image issues

I have created a theme, that I am not publishing. The thumbnail image is cut off on both the list of themes view and the more details theme view. I have tried every method to fix this that I could find from adding code to functions.php, and using various regeneration apps, to using setting=> media. Things actually got slightly worse. So now I have removed all the plugins and deleted the code, and then deleted the image and reinstalled it to the theme folder. Nothing is getting me back even the original error.
Even when I bring in other themes, the thumbnails have the same issue.
Can anyone help with this?

• This topic was modified 5 years, 5 months ago by bmajor.