There are 2 things you can do to fix the issue.
1. Update Novapress Pro, instructions on how to do that can be found here https://www.themely.com/novapress-pro-v1-0-6-released/
2. Regenerate your thumbnails with this plugin https://wordpress.org/plugins/regenerate-thumbnails/
That will fix your issue.
Let me know if you need further assistance.
