To know about why won't avast open, you can follow these steps below:
1. Go to the Properties Window of the Avast Antivirus program.
2. Go to the Logon Tab.
3. Click on the Browse Button.
4. Type the name of your account in the field- Enter the object name to select
5. Click on the Check Names button.
6. Wait till your Account Name appears.
7. Click on OK.
Hopefully, the above steps will help you to fix the issue if not you can also follow our blog on avast free antivirus won't open.