Getting the message “No plugins have been selected from the list. Please select at least one and try again.” while publishing the Custom Workflow Activity with Plugin Registration Tool?
When you are uploading your dll into the Registration Tool, the tool looks for any Plugin or Custom Workflow Action classes that are defined by your dll. In this case the tool is not finding any valid Classes in your dll, and so the ‘Select Plugin..’ list presented does not contain any valid Plugins to register.
Look the class definition where you have overridden the execute() method. The class must be inherited by CodeActivity Class. Declare the class as a Public class. And re-compile the dll and upload it to plugin registration tool and load.
You are done!