Initially, I installed Viber to my phone (2 years ago). Then a year ago, I installed it to my computer and a few months later to my tablet. After I installed it on my computer and tablet, the history of all messages were synced to all devices and whatever I did on any device, it was automatically available to all devices. That's the thing that I LOVE about Viber and that's why I use it as my default messaging app. However, I bought a new tablet and I installed Viber on it, but this time there's no history on it. It's synchronized with other devices since I installed Viber, but there's no history on the new tablet before the date I installed it.