Thank you for your reply. I Uninstalled the 2017 SDK and re-installed it from the download in the link you provided. I set it up the same way I have it set up in Revit 2016, in which it works fine. The attached image shows ...
- the install location of the 2017 SDK (default)
- the location of the AddInManager.addin file (C:\ProgramData\Autodesk\Revit\Addins\2017)
- the updated [TARGETDIR] in that .addin file (C:\Revit 2017 SDK\Add-In Manager\AddInManager.dll)
- the Add-Ins ribbon in Revit 2017 (top)
- the Add-Ins ribbon in Revit 2016 (bottom)
I don't get the warning message while opening Revit about a new Add-In when first placing the .addin in the directory. Nor an error about not being able to load that add-in. This is the exact same behavior I experienced in Revit 2015. But it works in R2016.
I will try placing the .addin in the other add-in directory. Then a reinstall of Revit 2017. Please advise, thank you.