Hi,
Is the rest service you created public accessible through the internet? I guess not.
So that is the reason, if you are using OutSystems in the cloud, the only way that OutSystems can consume your REST service is if it can connect to the computer (remote server) on which the service runs.
You need to host your service in the cloud, with solutions like Azure or AWS, or other solution.
Alternatively, if you do this on an OutSystems enterprise infrastructure you can request a VPN to be configured between the OutSystems cloud and your local network.
Regards,
Daniel