We came through this ‘NotFound’ message while running Ribbon Workbench in CRM 2015 UPDATE outside solution. Upon bit research found below article which explains this.
There is an issue with Dynamics CRM 2015 where if you open the Ribbon Workbench from the solutions area button and you are using the Server’s default organization it will give the ‘Not Found’ error. In this case you will need to open the Ribbon Workbench by double clicking on the Ribbon Workbench managed solution from the solutions list.
If your CRM server rejects your ribbon customizations, you will likely receive the ‘NotFound’ error message. Although the server does provide an exception message that is more helpful, the Ribbon Workbench cannot read the message due to technical limitations of supporting users inside a VMWare virtual machine environment.
To see the actual error message, you have two choices:
- Use Internet Explorer 9’s F12 Trace
- Use Fiddler
For more information, check the original post at above link.