I had a developer generate an html email for a client. This was the second version of the email as the previous one had a minor change. Then the client added the code into marketo for the email. But none of the module thumbnails show up? With the previous version the thumbnails didn’t show up either right away? It was like days later I went into the system to look around to see if I could find info on this and nothing? Then all of a sudden, days later, without doing anything, they thumbnails were suddenly there. Is there anything requites in the code to make the thumbnails generate? Or is it really just a matter of waiting an unreasonably long time for the thumbnails to be generated?