Menu Vanished

When editing the menus with the Supernova Theme the progress circle keeps turning. No progress is made.

I have the menu selected.
I checked the menu settings.
I checked the pages to be in that particular menu.
Clicked ‘add to menu’ and the progress circle keep spinning (several minutes and more.)

Tired this several times.
It happened when I made a new menu (for the footer). Now the menu below the header is missing.

Site is: http://www.thecreativetablet.com
Wordpress is updated

Suggestions?
Thanks,
John