When uploading an extension pack containing the requisite manifest.json.txt and json.txt files with syntax errors in the subdirectories, ArcGIS Maps for SharePoint returns the following incorrect error message, "Failed to add the extension package as the manifest file was not found."
最後に公開された状態: March 13, 2019ArcGIS Maps for SharePoint
Use the correct syntax in the JSON files. The real problem is the wording of the error suggesting the manifest.json.txt is not present, which is not true.