A test site running 6.4.15 is not getting anything when {{dc:post:the_content}} is used to pull in content. The {{dc:post:excerpt}} request works, so the problem appears to be with this reference specifically. I’m not sure if this is the same issue mentioned in this post:
{{dc:post:the_content}} stops rendering page content in Cornerstone.
That one mentions a fix would be provided in a upcoming release. I don’t believe a header or footer is causing the issue in my example. I tried disabling the header and footer to be sure. Please let me know if there is a solution for this. Thanks.