I have wiped all my data from device and updated it, installed Avast Mobile Backup and it created a new device on my.avast.com, how to connect my device to previously generated device on my.avast.com?
The simple answer is that you can’t.
You can add a device (as you did) or remove a device.
Combining devices wouldn’t make sense.
It would mean that you multiple devices will be seen as one while they are separate devices.
Just remove the old one from your account.
If you install the backup on new device, in my.avast.com you can restore the device from your previous device to the new one.