Our developer have checked your site.
First thing to do was to replace the template with freshly downloaded, but it didn't helped showing that the problem is somewhere else.
On your site you have uninstalled k2 component, but it's items are still showing in menu editor - that might be the cause of the problem. If your database have lost its integrity it might be hard to make anything work correctly (currently standard Joomla api doesn't provide menu code, either it is Main Menu or Top Nav menu selected).
I would suggest to start with clean quickstart installation and port articles by copy paste from old site (remember to use different database for new quickstart).