"Image URL cannot be found" Error for Editing Images in Emails

-Error editing image in email: “image URL does not exist” or “image URL cannot be found”

 

-SSL not enabled on Marketo instance
-Browser blocks unsecured content

Option 1
-Set up SSL for landing pages (Recommended!  SSL should be a baseline configuration for all landing pages and tracking domains).
Add SSL to Your Landing Pages | Adobe Marketo Engage

Option 2 (Not recommended!   Warning! This is a security risk.)
-Allow browser to view unsecured content (can choose to turn this setting back off in the browser after viewing the content)

This link below describes how to enable this content in Chrome.
https://docs.adobe.com/content/help/en/target/using/experiences/vec/troubleshoot-composer/mixed-content.html

This link below describes how to enable this content in Firefox.
https://support.mozilla.org/en-US/kb/mixed-content-blocking-firefox

Option 3
-Try to use a different browser or try turning off all browser extensions.

This issue could be caused by SSL not being enabled.

If the issue was sudden, and SSL is enabled, it is likely due to the browser needing an update. Check if there are any updates that need to be done.