Designer is not able to upload and preview this (newer?) file type:
AMPHTML Formats: ZIP containing 1 HTML doc and up to 39 media assets
Max Size: 150 KB
We’re looking into using a new ad format for digital banner ads called AMPHTML.
They’re animated but basically consist of an html doc with a bunch of supporting files and code. I made a few attempts at uploading various things into a Workfront job to preview it but nothing worked.