OK, you don’t say what Windows or Avast versions you are talking about.
Avast is a resident, on-access antivirus and part of its scanning modules uses an internet connection to check out unknown files, etc.
Avast also really does require Internet access to be able to keep the Virus Definitions up to date or it too could be as much use as a chocolate teapot. Or it will keep stating that your Virus definitions, etc. are out of date, that would require you to periodically download the full virus definitions database (from another PC with internet access).
DavidR and bob3160 were right to be dubious about the answer given by MartinZ here.
I think that the simple fact that avast requires a connection to activate a free license answers their questions: avast free continues to be not totally free, which makes no sense contrary to what MartinZ announced.
If only that were the case, as we continue to see cases like this in the forums, hopefully this new offline installation file will see an end to this. That said the OP hasn’t got back to the topic to answer the questions about what avast version/build he installed.
Presumably the off-line installation file (from wherever source they got it) was used on this off-line computer.
was a bit radical.
Unless you know which Avast version and OS are used by tonywcaddick (as requested by DavidR) , it's quick to answer that he needs to be online to activate his license.
V20.8 offline with W10 by exemple should not require a connection.