have you tried avast repair?

controlpanel > ad/remove programs > avast > uninstall/change > repair option

you have of course removed previous used AV and used that vendors removal tool
General: Uninstalling a third-party antivirus software https://www.avast.com/en-eu/faq.php?article=AVKB11#artTitle

avast support https://support.avast.co > submit a support ticket