FileMaker 12 Server Advanced shipped with the known limitation of only allowing layouts using the classic theme to be available through Instant Web Publishing.
To allow your database to use Instant Web Publishing, connect to your hosted database using FileMaker Pro and change the layout theme to classic.
More information is available here:
http://help.filemaker.com/app/answers/detail/a_id/10766/~/instant-web-publishing-with-filemaker-12
- 1 Users Found This Useful