firewall problem

My firewall won’t switch on and neither will my internet connection. When I run a full scan it says threat detected then to run a full system boot. This had been running for the last 3 hours. How do I fix it

For a start post in the correct forum and provide details.
This forum is about the https://my.avast.com website.

For Avast Free/Pro/Premier you should be here:
https://forum.avast.com/index.php?board=2.0