When trying to add a new Server script, by opening the Script Editor and selecting the ServerScript > the Add Scriptlet button does not become active. It stays grayed out. Same happens with ClientScript and ServerScript
When right clicking on either of them and select the option New Scriptlet from the drop-down menu, nothing happens. No new script can be added.
Click on Server Script tab. If the editor is empty, means somebody accidently deleted the default definitions. To fix the issue, copy there the following lines
// ScriptType: ServerScript
public void Dispose()