A message “Invalid zip file.” appears in response to a trial of the registration of an HTML file.

HTML delivery by Smart Catalog requires that resource formats satisfy the following conditions.

・HTML resources have been zipped into one file.
・An index.html (fixed file name) file exists immediately under the zipped directory.
・The above-mentioned index.html acts as the top page (initial page), and the HTML resources operate systematically.
・HTML resources can operate under the Safari browser on the iPad.

Please refer to the following manual.
【Web】7.15 Setting HTML Content