Long time ago I did something with this, but from the top of my memory: This module creates a REST webservice first. Then the result of this webservice was converted to a csv file. Are you sure that you have used the microflow MF_StartCsvServices as an afterstartup flow? Because it seems it can not find the created REST service.
Regards,
Ronald
[EDIT] Note also that the current (latest) version on Github is already converted to Mx7 which is not yet out. So you should also check the version you use because I do not know how backward compatible this is.
[EDIT2]
Did you enable the request handlers? Because the errro tells you it can not find the rest service. And you do not need the rest module. Rest is now incorporated in the modeler.
The ws-doc part of the url was a work-around for the fact that you couldn't create new request handlers paths in sandboxes. That has been fixed, so i've modified the ws-doc path to be csv now.
Your curl command should be:
curl -v -X POST -H "Content-Type: text/csv" http://MxAdmin:1@localhost:8080/csv/Orders/ProductLabels --data-binary "@labels-data.csv"
I've updated the docs on github, appstore publish will have to wait until mendix 7 has been released.