Hi About two months ago this problem started Please help
Do you get any error messages? How do you notice that it is not working?
What Avast version are you using?
There are many such topics in the forum related to Boot Time scans. The New Boot Time scan run under the Windows Runtime Environment (WinRE) introduced around the end of July 2022, in Avast 22.7 - https://forum.avast.com/index.php?topic=320488.0 had an issue for some.
However, without exact details of which product operating system and version this is speculation.
work around here to revert back. link on 6th post https://forum.avast.com/index.php?topic=320945.0