We propose that you use the Avast Setup wizard to fix your installation in Avast Antivirus. Follow these steps to repair your avast antivirus software:
Make sure your computer isn't running any other programs or antivirus software.
Select Apps and Features from the menu that appears when you right-click the Windows Start button.
Select Apps & Features on the left side, then pick your Avast Antivirus version and select Uninstall.
If the User Account Control dialogue asks for permission, choose Yes.
Click Repair when the Avast Setup wizard opens.
To authorize the repair, choose Yes.
Wait while the setup is being repaired. Avast Antivirus on your PC