this happened to me too several weeks ago when installing the free version on another computer, there was no way to register from the UI. Only way out is to go to Avast web site and request a registration code for the free version. Comes through mail after a few days.
I agree with you, but in the case of registering, as in the issue in this thread, the Repair does not fix the problem as I have tried this on several machines and it does not work. I’m beginning to think it may be a server issue as well. But the email responses are beginning to come quicker now.