Problem notifying a specific user through push notification

I want to send a notification to a specific user through the push notification REST API. I am able to use the web console to send the notification to a particular user I am also able to use curl and send to a specific token or to broadcast to the whole channel. The code below works

curl -b cookies.txt -c cookies.txt -F "channel=<channel>" -F "to_ids=everyone" -F "payload=test" https://api.cloud.appcelerator.com/v1/push_notification/notify.json?key=<key>

And this one with a specific user_id doesnt work

curl -b cookies.txt -c cookies.txt -F "channel=<channel>" -F "to_ids=<user_id>" -F "payload=test" https://api.cloud.appcelerator.com/v1/push_notification/notify.json?key=<key>

I do get a successful response from all calls, but the device never gets the notification. Note that that same user_id is able to find its way to the device when sent from the web console.

Thanks