I am running Win XP. I updated my Avast free software. It is asking me to register. When I click on REGISTER, it try’s to load. Then I get a screen that says " The online content is unavailable. " Please advise. Thank you.
Best is to perform a clean installation:
https://forum.avast.com/index.php?topic=169255.msg1203279#msg1203279
There are some issues known on some systems when upgrading that are solved with a clean installation.
See if this solution is working for you.