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."
Last Published: March 13, 2019ArcGIS Maps for SharePoint
Bug ID Number
October 16, 2015
April 5, 2023
ArcGIS Maps for SharePoint
The bug has been fixed. See the Version Fixed and Additional Information, if applicable, for more information.
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.