I have a site durham.totalsportsmagazine.ca that is constantly being updated but once and awhile I have photos that worked fine for weeks suddenly get greyed out on the desktop version. It seems this happens when the photos get to the middle of the page when new content is added at the top. I have replaced the photos and even renamed them but they remain greyed out. If I put an entirely new photo in the same box, it works fine. Any ideas??
If the issue occurs again, see if you can share some screenshots as well, and test in different browsers too. Let us know which browser & version (if the issue is browser specific). Also show us a screenshot of the same image in the site (before you replace it).
Lastly, ensure you have updated Muse to the latest version.