I have managed to install version 2.4.0 and it works correctly. But even uninstalling the Revit plugins I have not been able to get any later version to work.
Thanks for trying that, it is actually very helpful, I think I’ve found the culprit to be indeed a conflict with another addin. There are other locations in which Revit addins could be installed:
User Addins:
%appdata%\Autodesk\Revit\Addins\
%appdata%\Autodesk\ApplicationPlugins\
Machine Addins (for all users of the machine):
C:\ProgramData\Autodesk\Revit\Addins\
Addins packaged for the Autodesk Exchange store:
C:\ProgramData\Autodesk\ApplicationPlugins\
Autodesk servers and services:
C:\Program Files\Autodesk\Revit 2016\AddIns\
Here are my findings cc @connor
Version 2.4 of the connector and earlier used v1.3 of the Revit.Async library: