See this topic - https://forum.avast.com/index.php?topic=327907.0 - in the General sub-forum https://forum.avast.com/index.php?board=1.0
Which is I guess the same issue, though they didn’t attach an image.
"Avast has blocked access to hXXps://uci.edog.cdn.office.net/ because one of the issuers of the [i][u]server certificate has expired[/u][/i]" and the other one had "support.content.office.net" listed as the website.
I have broken the link in the quote above and also highlighted the reason. I’m not sure what can be done about this expired certificate, other than MS updating the certificate or adding an exception (obviously there is a risk involved) to allow access.
Note I’m an Avast User and not an Avast Team member.