WhatsApp chats disappeared after Android Operating System Update I am having a Moto E XT-1022 (1st generation) 2014 model. In order to update its OS from 4.4.4 to 5.1, I had to make 500MB space available so I deleted all WhatsApp database backup files without copying them elsewhere as I knew from my own experience that WhatsApp had nothing to do with Android OS upgradation process since I had already upgraded the same android from OS 4.4 to 4.4.4 and my old Samsung even before that without losing any of my WhatsApp messages but unfortunately, this time all my chats are gone after OS update.   

As I thought, WhatsApp tried to take the backup automatically on 3 AM like any other day, but it's not working either. Now I'm left with a possibly corrupt file msgstore.db.cypt8 (size: 103.62 MB). I read somewhere in here that there is a possibility of mending the corrupt backup and regenerating it afresh if the key can be extracted somehow. So is there any ray of hope for me?

PS: Mine is a non-rooted device.
The only one that can help for this kind of issue is WhatsApp. You may want to contact support@whatsapp.com (Source: https://www.whatsapp.com/contact/) and see what they can help you with.


  I just can't afford to lose my three years' important data.


This is the root of your problem. Any important data that you can't afford to lose shouldn't be stored as instant messages, you should have copied over any important data elsewhere.