Hello Aun,
Thank you for contacting support.
This usually occurs when there is a connectivity issue involved with your device and our servers. Please try using Tango on both 3G/4G and Wireless. If the problem persists, try connecting to different networks as some may use firewalls that block ports that Tango requires for communication.
Please feel free to reply to this email if the issue is not resolved.
Bests,
-Zyra | TangoMe, Inc.