Your error message indicates that it is looking for Office 2007. When you installed Studio, you must have selected Office 2007 instead of Office 2016. You'll need to re-install Pega Robotics Studio and be sure to select the correct version of Office when you install.
We did reload Pega Robotics Studio and selected Office 2016. It still gave the error. One other tidbit was that Office 2010 was actually selected earlier, so it seemed odd that it would want Office 2007.
We first changed the Runtime and Studio config.xml files in %appdata$\OpenSpan and in the c:\Program Files (x86)\Openspan\OpenSpan Studio for Visual Studio 2015 folder, as well as copying the contents of the Office 2016 folder to the c:\Program Files (x86)\Openspan\OpenSpan Studio for Visual Studio 2015 folder. When that didn't work we decided to reload.
Are you getting this error running from Studio? Can you please post a screenshot of the property page of OpenSpan.Office.dll in C:\Program Files (x86)\OpenSpan\OpenSpan Studio for Microsoft Visual Studio 2015? I'll attach mine for reference. On the details tab it shows what version it is for.
Can you create a new solution and add an Outlook Connector and set it to run on Startup? I'd be curious to see if it gives the same error.