I accidentally uninstalled viber but I cant now re install it on the same device I accidentally uninstalled viber but I reinstalled it again. Now I cannot setup the old account on the same device. The viber version used by me is 5.3-the latest version. I previously used viber on samsung galaxy tab 2 with os jeally bean -4.0.4.  I send email to the viber forum but that did not solve my problem. I previously used the same version on my tablet. Every time I enter my phone number error message pops up. I was tninking of activating my viber account on another device and deactivate my account . And then using the same number and device I wish to setup the viber account once again. Will that help???
Go to settings clear cache, etc, n uninstall. Then reinstall as usual. :-) hope this helps.