Have you tried to uninstall viber to reinstall it to fix the problem since it is not working properly? But when you go to control panel Viber won't uninstall after clicking Uninstall button , it says fatal error during installation , so why is this happening and how to fix it ?

I think you might have tried many ways to get rid of Viber
completely since I searched its removal guides from Google on the internet. However,
most of them are not helpful or complicated. Fortunately, I have found an useful Viber removal tip to solve the problem successfully.
So I could avoid that trouble if I could carefully follow the software
uninstall guides step by step in this post.