I developed a Word 2016 Add-in using Visual Studio 2015 + Office 2016. I've recently moved to Office 365, since the MSI version of Office 2016 doesn't support the new features of Word API library.
As I opened the project and tried to run in debug, I noticed that it wasn't working. Word opens showing this error message inside the add-in taskpane:
Error : "This add-in is no longer available: addin inserted during development are only available during debugging from visual studio. Please open your project in visual studio and re-run your application or deploy your add-in into a valid catalog and reinsert."
Also the published version of the add-in - installed from a shared network folder - isn't available anymore: the manifest isn't listed in Insert > Store > Shared Folder dialog.
After some investigations it turns out that if I replace in manifest every occurrence of my custom namespace with the default "Contoso", everything works fine:
<Title resid="MyCompany.GetStarted.Title"/>
<Title resid="Contoso.GetStarted.Title"/>
...