This is mainly caused due to two reasons.
1. Due to your WiFi firewall settings.
2. Viber service is probably down at Amazon servers end.
Go to settings > applications > all > viber > clear data
Restart your mobile. Now viber should work fine!
If not, Please have the systems administrator go to the WiFi firewall settings to make sure that the below ports are open for both sides:
1) TCP 5242
2) TCP 4244
3) UDP 5243
4) UDP 9785
2. For second problem, there is nothing we can do but to just wait for them to fix it.