If it has previously updated for you then there should be no need to change any of the connection settings, i had this problem the other day with the new beta and a repair then a reboot fixed it.
Also as Pondus has mentioned please make sure that any remnants of old av’s including the one that would have come on your system when you bought it have been removed properly with the correct removal tool which you should be able to find within the link that Pondus has supplied.
Also if you are using a third party firewall to make sure that all avast processes are set to allow all.