UPDATE:
According to a couple of different plugin developers (Awesome Support and Easy Digital Downloads), you need to fix your plugin’s use of PHP sessions.
Basically any other plugin that utilizes PHP Sessions conflicts with WordPress PDF Templates functionality, sometimes only when the FETCH_COOKIES_ENABLED
is set to true, and sometimes REGARDLESS of that constant.
Apparently, WP PDF Templates doesn’t work AT ALL when Easy Digital Downloads is also installed. That should be a big red flag for you, as EDD is a HUGELY popular plugin and very widely used. It is also created and maintained by a well known and accomplished plugin developer who is considered to be an authority on WP plugin best practices, clean code, and quality plugins.
Please read this support thread to better understand what I am talking about.
A fix would be great ASAP, so that I can continue to use the Awesome Support plugin in conjunction with your PDF Templates plugin.