Your microflow expects a parameter, so you need to make the parameter available in the context of your button. So you need to have for example a dataview with page parameter or a (nested) dataview as context for your button. I can imagine your dataview NPE has a flag, controlled by your button. Based on this flag data will/should be send or not.
If this is not possible, you can create a custom microflow which does not expect a parameter. You can trigger this microflow via your button, but, you need in that case to do the logic without a passed context (read: parameter) to toggle sending data.