Click the AdGuard icon at the Menu Bar - go to Advanced - Reset settings... and quit AdGuard.
In the Spotlight Search, type Terminal - enter sudo rm -R /Library/Application\ Support/com.adguard.adguard
and execute
Restart your computer.
Open the Terminal again, type ls -al /Library/StagedExtensions/Library/Application\ Support/com.adguard.adguard/
and execute. You should receive the following: No such file or directory