Jungleland: background image to nav bar

I have installed the Jungleland theme on a blog https://www.rainbowresolutions.com.au/samantha/. However I am having trouble getting the background image for the nav bar to stretch across the width of the menu item. Currently it only shows up as a narrow vertical bar to the left of the current menu item. I made sure the CSS was set to repeat-x and I also widened the background image but no luck. Maybe there’s something else which is overlaying it? I can’t quite see what.
Thanks for reading, hope someone can help.