I have tried all your suggested approaches and no luck
I wanted to add the installed DLL-file manually from the "COM Add-ins" window but none of the files I choose are accepted by MS Word.
If I run the file Docx4jHelper.vsto I get the error message below. Not sure what is means because the file is available in the folder.
Name: Docx4jHelper
From: file:///C:/Program Files (x86)/Plutext/Docx4jWordAddIn/Docx4jHelper.vsto
************** Exception Text **************
System.Deployment.Application.DeploymentDownloadException: Downloading file:///C:/Program Files (x86)/Plutext/Docx4jWordAddIn/Microsoft.Office.Tools.Word.dll did not succeed. ---> System.Net.WebException: Could not find file 'C:\Program Files (x86)\Plutext\Docx4jWordAddIn\Microsoft.Office.Tools.Word.dll'. ---> System.Net.WebException: Could not find file 'C:\Program Files (x86)\Plutext\Docx4jWordAddIn\Microsoft.Office.Tools.Word.dll'. ---> System.IO.FileNotFoundException: Could not find file 'C:\Program Files (x86)\Plutext\Docx4jWordAddIn\Microsoft.Office.Tools.Word.dll'.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath)
at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy)
at System.Net.FileWebStream..ctor(FileWebRequest request, String path, FileMode mode, FileAccess access, FileShare sharing, Int32 length, Boolean async)
at System.Net.FileWebResponse..ctor(FileWebRequest request, Uri uri, FileAccess access, Boolean asyncHint)
--- End of inner exception stack trace ---
at System.Net.FileWebResponse..ctor(FileWebRequest request, Uri uri, FileAccess access, Boolean asyncHint)
at System.Net.FileWebRequest.GetResponseCallback(Object state)
--- End of inner exception stack trace ---
at System.Net.FileWebRequest.EndGetResponse(IAsyncResult asyncResult)
at System.Net.FileWebRequest.GetResponse()
at System.Deployment.Application.SystemNetDownloader.DownloadSingleFile(DownloadQueueItem next)
--- End of inner exception stack trace ---
at Microsoft.VisualStudio.Tools.Applications.Deployment.ClickOnceAddInDeploymentManager.DownloadAddIn(TimeSpan timeout)
at Microsoft.VisualStudio.Tools.Applications.Deployment.ClickOnceAddInDeploymentManager.InstallAddIn()