Label rule failing

I have activated an LPN label type for the label generation business flow.  I have a label assigned as a default that I want to print only if the order type is an internal sales order.  I set up a label rule that basically says print a ‘no print’ label if the business flow is ‘lpn generate’ and the order type is ISO.

This rule isn’t working.  The LPN type default label is printing every time I generate an LPN regardless of the order type.

Does anyone have any suggestions on how I can prevent the default label from printing when the order type is not ISO?