Do you have any additional details you can provide? Also, you should just be able to call RaiseEvent to trigger the OnClick event. Have you tried that?
Calling Invoke script requires the script name and the ability to supply any parameters. Some scripts use parameters you cannot easily provide via the method (such as the this property of an element). In that case, I would use execute script to create a duplicate function that calls the original one passing the parameters I couldn't provide in the automation.