Can you send me a screenshot of the URL you are entering (if you dont want to post this in the thread you can PM me the image)? What type of authentication are you using in your portal? IWA?
I have issues with ArcGIS for Mobile 10.2 and Portal 10.2 while using IWA.
(First i've fixed the featureservice to become a mobileservice aswell, becuse its not supported in the portal yet.)
Everything works great as long as the services are "public". But if i try to set permissions to certain Groups or just to the Portal everything failes becuse of invalid token.
With Mobile Project Center: I can see on the traffic that a token is created. (referer: www.esri.com) Thats really correct? And it tries to access the service with that token.
If i turn off the security. Creates a Project, deploy. Turn on the security again i cant even create a token with the Mobile application. Only get a 401 error while trying to access /arcgis/sharing/generateToken/generateToken