When you upgraded to windows 10 did you update Avast at all or did you just leave the previous version installed ?

For info I have AIS on windows 10

Download Avast Uninstall Utility to your Desktop.
Download the correct version of Avast
Avast Free
Avast Pro
Avast Internet Security
Avast Premier
Disconnect from the net
Uninstall Avast via control panel

[]Run the uninstall tool and accept the reboot to safe mode
[
]Once complete reboot your system
[*]Reinstall Avast