My old phone just died on me yesterday. It used to backup the Whatsapp chat history to my main google account, which I also used to register the device.
Now I have a new phone, and I registered it to the same google account. After installing Whatsapp, I tried to restore the google drive backup to the new installation. However, when I try to enter my google account, it tells me "This account already exists on your device"
Somehow after switching apps, Whatsapp assumed I don't want to restore a backup, and now I'm stuck with no history.
Also, when I try to setup the google drive backup on my new device, it gives me the same error when I try to enter my google account; "This account already exists on your device". I can't figure out what I am doing wrong. Is it just impossible to backup whatsapp to an account already registered to the same device?