When I had my A8, it was running on wifi – so that should not be a problem.
The problem is your new router/the settings.
Hard to say anything, when one does not know the brand, the settings, the strenghts of the signal.
After resetting it, I would try connecting it with a cable – that some times helps and can give you access to the menu for the wifi password.
Use the Bang & Olufsen app to set it up.