Hey Erica,
the last file I sent you was not intended to alter the image, it was to fix a small bug that I found at the same time; sorry for mis-communication :)
As to the issue, please try removing and re-uploading the thumbnail for the project in question – the mechanism that displays the project box background image takes the latest of all images attached to a particular project, including both the images in the content and the attachment (in WordPress, all of them are considered attachments). Let me know if this helps!
Sincerely,
Andrii / Satori Studio