Avast free antivirus build 17.8.3705.249 refuses activation

[fmolina]

Dears,
Avast free antivirus on windows 7 x64, fresh install on a virtualbox VM. Installed last version, after a few days a red cross appears on the tray icon, and the UI says that I am unprotected ant the licence is not valid (see attachment #1). Click on "Activar" (activate), leads to choose between free and paid (attachment #2), selecting paid gets the screen offering trial version (attachment #3), but after dismissing this (either clicking No, thanks or closing the window) nothing happens, the red cross stays there, even after rebooting.
- Tried uninstalling with avast clear in safe mode and reinstalling: after a few days, red cross again.
- Tried repair via control panel: it offers me two buttons for avast: uninstall or change. Clicking any of them appears a window telling to renew license (attachment #4), but after click on "Volver a avast antivirus" (Back to avast antivirus) anothe window telling reneweval is done apperas, then everything is equal: red cross still there.
I did not find in the forum anything of help.
Please advise.

[fmolina]

One more thing, do not know if it is related or not: here we are behind a proxy, updates work ok, but I have to use the offline installer, the online one does not seem to work.

[mchain]

Activation requires an internet connection as does the online installer. 

Try temporarily removing the proxy connection (write your settings down before reverting) and establish a non-proxy connection.  This should work unless you are behind a nation-state firewall for which avast is not permitted.

[fmolina]

I cannot connect to internet directly. However, in the past all worked perfectly. And, besides, I do not understand why free antivirus requires activation. as it was announced that it would not be required anymore.

[REDACTED]

Same thing here - virus and program updates work fine behind our proxy (after adding proxy IP and port to the Avast update settings) but activation simply won't work. And indeed, to install you need to download the full version.