Hello there, thank you for your post, let's see if I could be of some assistance.
I will need some more information before I can see what I can do to help, such as:
-What operating system you're using: Windows 7/8/10? - 32/64 bit?
-What version of Avast Secure Browser do you have installed (You can click the "3 dots menu" on the top right of your browser window -> "Help and About Avast Secure Browser" ->"About Avast Secure Browser")