Firefox - Update/Save Password Box Not Showing Properly After Login, Blocks Page

I’ve been having issues with my Firefox add-on. It fills in the username and password for me with no problem, but once I log in it tries to display the box for updating or saving a password. The problem is, the box doesn’t show, but the iframe displays over the entire page and I can’t click on anything unless I go into the web inspector and set it to display: none. So I can’t update any of my passwords or save new ones, and I have an extra step to deal with every time I log into a site.

I have the latest version of Firefox (58.0.2) and Avast Passwords (1.1.3084). The only other extension I am using is AdBlock Plus, which is also up to date.

Any ideas for how to fix this?

Thank you so much!!!

Here’s a screenshot.