In Preferences > General > Browsing can you please take a screenshot of your settings?

The screen shot icon is not visible when I am in my Preferences page. But I have 4 browsing options, if that helps? -Auto scrolling -Smooth Scrolling -Always use the cursor keys to navigate within pages -Search for text when you start typing. I have smooth scrolling selected, but auto-scrolling didn't seem to make a difference either

This can happen if you use a GTK 2 Linux theme. Current Firefox version require a GTK 3 compatible theme.

Is it possible to update to the newer compatible theme?

Not in Firefox but on your Linux distro. GTK3 themes may be available to install in your package manager or you can get them from say https://www.gnome-look.org/browse/cat/135/ord/latest/

The official builds of Firefox since 46.0 have required GTK 3.4 (three.four) at minimum to run and as a result needs GTK3 themes to theme Firefox. Some Linux distros may have delayed this change with their own packaged builds of Firefox until more recently.