Hi,
I'm an official representative from Viber. I'm here to help :)
Please make sure that both you and your contact have the latest version of Viber installed.
In addition, it could be that the network you are connected to is blocking Viber's traffic.
1. First, please try uninstalling and reinstalling Viber when connecting to a few different WiFi networks (in order to pinpoint the source of the problem). What are the results?
2. Also, please make sure the following ports are enabled ("forwarded") on your routers or firewalls:
TCP: 5242 + 4244
UDP: 5243 + 9785
(if you are not sure how to enable ports, you may contact your router manufacturer or your Internet Service Provider)
* If it still fails, please specify what country you're located in, and which cellular network you're subscribed to.
If you have any more questions, please feel free to let me know :)
10-20-2013 05:35 AM