Indeed the error is misleading. Basically RoboHelp is advising that it doesn't understand the installed version of Word. Certainly Word in the 365 is newer, but RoboHelp won't understand how to work with it.
You should definitely consider upgrading to RoboHelp (2015 release).
To chime in; Office 365 is interesting since there are multiple projects that you may be talking about. It includes the web apps, which are browser based versions of Word, PowerPoint, etc that run in the cloud. But most subscriptions also provide you with the desktop version of the programs. Since it's a subscription, you get the latest version as soon as it is released. (Currently 2016)
RoboHelp requires Word to be installed on your computer. So if you only have the web apps, it won't work. Most of the time, you also get the desktop versions. If you are using 2013, you can use RH11 or below. If you are using 2016, you need RoboHelp 2015 (patch 1).