Before you download Viber application you have to make sure that your computer meets the system and hardware requirements. To view these, you can visit the following web page. To obtain an official copy of Viber program, you can visit Software Informers web page in order to obtain a download link or visit the following official website. If you cannot download the program using your current browser, try with a different one(ex Internet Explorer, Chrome, Firefox).
However, if you still have problems downloading this product, make sure that you didn't blocked it by mistake with Windows Firewall or with your antivirus program.