If you load a template and the body comes up empty, it can be for one of two reasons.
First, if it is an HTML Only template, and you don’t have a plain text version, we can’t read the template. Please change your format to either just Plain Text or to HTML and Plain Text (and include a plain text version).
The other reason is that if you sent a broadcast email from a template in Infusionsoft, that broadcast will show up in the list of templates and appear as a duplicate of the original template, but won’t work correctly. This is confusing and is a known bug with Infusionsoft. Simply choose another variation of that template with the same name and it should load correctly.