UX Builder not saving changes

I have bought Flatsome’s WordPress theme the other day. And I tried to fix my homepage by using UX Builder.
I selected my favorite background, and then I pressed “Apply” button. Next,I pressed “Update” button, then I tried to leave this page. But the warning “Exit? All changes since last save will be lost”, and my correction that I have made was not saved and reflected.
What should I do? What do you think is a problem?
Please teach me.
I am waiting for your reply.

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