Link is broken when clicking from the homepage

I changed the slug for my ‘Teach in China’ page and now when I click on the link in the header on the homepage, it’s a broken link but when I click on the same link in the header on any other pages, it works fine.

I have no idea why this is happening and it is driving me crazy. Please please help me understand why this is happening and how I can fix it.

Thank you.

The page I need help with: [log in to see the link]