Keyboard navigation through results no longer working

Hello,

When I first installed this plugin I was able to keyboard navigate through the dropdown list of results by pressing the up and down keys. But now it only lets me go to the first result. If I press down again it loses focus from the field. You can test this on the page itself by typing the letters “plu” into the search form and then pressing the down key in the results.

Any idea why this might be happening?

Thanks for shining any light

The page I need help with: [log in to see the link]