Sub Menu broken – help

I have set up my main menu under the name ‘Standard Menu’, which i’ve specified both in the admin menu panel, functions.php and header.php, but my submenu’s are not being generated. I’ve checked the depth and it’s set to three (3). I’ve googled for a few hours but all solutions that I find have to do with css or html issues (something is generated and it is not showing up correctly) vs. something is not being generated. I’ve checked my menu and it’s named correctly, it has three levels of menu (Parent, Child, Grandchild), but only the parent is generated.

You can see here by clicking on ‘special’ in the menu, no drop down appears.