There is a known issue between the AVAST real site protection feature and CleanBrowsing. You will need to choose which one you prefer to use. AVAST and CleanBrowsing can exist, but you can’t have two platforms doing the same DNS based content filtering.
Why The Conflict Exists
Every time you enter the URL (address) of a website, such as www.example.com, into the address bar of your browser, the URL is translated to the IP address (Internet Protocol address) of the web server where the web page that you want to access is stored. Real Site provides an encrypted connection between your web browser and Avast’s own DNS server to prevent hijacking.
In other words, Real Site hijacks your DNS and uses it’s own DNS resolvers. CleanBrowsing is also a DNS resolver and there in lies the problem.
Disable Real Site Protection
To ensure your full security, Real Site is enabled by default.
To disable Real Site, go to:
Protection ▸ Real Site, click the green (ON) slider, and select a listed time duration, then click OK, Stop.
The slider then switches to red (OFF). We recommend you turn this feature off permanently by selecting the Stop indefinitely option.