To solve the Avast error, you should disable the Microsoft services. Then, you should disable the startup tab tasks.
After the system has finished performing these tasks, you should restart your computer. The next step is to enable the Avast service again.
Then, click the "Restart" button. Once the system has been restarted, your Avast software will open easily without any more issues.

Still your Avast is not opening? You can also check various methods here: https://cleanersuite.com/avast-wont-open-on-windows-10-how-to-fix/