As far as I'm aware it is an automated process so it shouldn't matter it being a weekend. What version of avast are you using?
Are you using an anti-spam program or is your ISP using one?
What date is your registration due? - if you have a little time a week or so, give the process of sending you a new registration a day or so. If it is very urgent, try registering again and use a different email address (if you have one) and temporarily disable your anti-spam program (if you have one).
