Strange, I'm not sure what to suggest. I've retested each of the emails under the presentation tab as Text and as HTML and it seams to be working completely fine there. I've checked the code and I don't see a reason the content plugin wouldn't work there.
Within Extensions > Plugins filter by "system" plugins then sort by "Ordering ascending". This gives you the current load order for system plugins. Next move cbsubsbot to the very top so it loads first as sometimes it's a conflict with another plugin that causes issues.
Try a simple usage like the following and see if it works.
Code:
[cbsubs:if plan="3" status="A"]TEST[/cbsubs:if]