Parallax effects not working on WP ver 5.2.3

I have installed the plug in on a local development machine running WP ver 4.9.11 and it works great! I have a test site running on a SiteGround server running 5.2.3 and the Parallax functionality does not fully work. What I’ve observed is this:

* If I use the Visual Editor (e.g. not Gutenberg) and add in a Parallax image using the AWB button, the scroll option works in so much as it places a static background that does not move when I scroll the page. It does not do the “scroll at a slower speed than foreground” behavior I would expect. All others options (Scale, Opacity, etc) do not work. They simply add in an image to the background that moves when the page scrolls (e.g. normal background image behavior.) (One point here – I am disabling Gutenberg by using the Classic Editor plug in. I re-enable Gutenberg by deactivating that plug in.)

* If I use Gutenberg and add in a AWB block, no Parallax options work – I just get a background image that scrolls with the page (e.g. normal background image behavior.)

I’ve tested this on Safari ver 12.1.1 and Chrome ver 77 on the Mac.

There are, of course, other differences between these two sites but the WP version number is the main thing I can think of. I’ll be very interested in any suggestions.

Thanks!