I followed the instructions at https://blog.avast.com/2014/04/03/how-to-reset-your-avast-administration-console-password/
The first time it seemed to work but when I tried my new password it still would not let me in. I restarted my computer and still could not get in. I tried the reset again and got an error:
Cannot initialize data source, error 0x80004005
Cannot reset the password, error 0x00000001
I did run an elevated command prompt.