@ AndreaVr
The beta build 11.1.2234 of avast 2016 hasn’t had all languages localised yet, that will or should be done before avast 2016 goes live.

The 1033 language module is English - I don’t know if adding English to your Languages list might help resolve this particular issue (avastUI > Settings > General - Language - Install additional languages.

Have you tried logging on to your my.avast.com account using your browser as I have suggested many time ?

Or

If I use the Add New Account option (as in my attached image above) then I too get the message 'The online content is unavailable.' But if I use the Manage Accounts, it recognises me and the my.avast.com account I'm connected to. If in this screen I can click the Add new account and with that I have a login screen - this I can enter the my.avast.com account I already have.