Usually, activating Viber does not present a problem. However, in some cases, the activation can somehow get stuck. Sometimes this is the result of the country you’re in and sometimes this is due to your mobile carrier or service operator. Fortunately, there is a solution.
During the installation process, you should get your access code by SMS. If you don’t receive the SMS within 1 minute, you can try pressing the “No code?” button which will guide you through an automatic call procedure. Accept the call, write down the access code and enter it into Viber.
If the automatic call does not work, whether that means you did not manage to get through or you did not get the code when you called, try uninstalling Viber and wait for 24 hours. After that period, try installing it again from the begining.
If even that does not work, you can post your problem at Viber Support. There is a wizard which will guide you through the process. Finish the wizard and the support team will contact you in a few days.
If you have 2 SIM cards in a single phone and you are having problems, please check: How do I install Viber.