Firefox on iMac does not populate user name and password from Avast Passwords

I’m sorry if this has been answered before or is trivial. I’m totally new to the Mac world. I used Avast Passwords in Windows for years and it was very reliable. The problem is, although I have installed Avast Passwords and it is integrated with Firefox, nothing ever appears in the fields on the pages. I always have to look them user name and password up in Avast and then paste them manually.

macOS Mojave 10.14.3
Firefox Version 65.0
Avast: I can’t figure out the version, but I downloaded and installed it 2/8/2019.