Off canvas menu not displaying

Off canvas menu not displaying

Used this great extension many times, though, always open to the fact I did something dumb! :-)

When I first set it up, it worked flawlessly. Something I've done recently, not sure what as I'm rebuilding the site and doing a lot!) has stopped it displaying. Now, when I click the hamburger icon, the screen gets the semi-opaque wash that it should, but the menu does not slide out (www.ckdev.inf/cp).