font no applied

Hello,

In theme menu of Max Mega Menu, I choose “Open sans” ‘font in Menu font family setting which is in general settings but this font is not applied.

However, if I change, for exemple, background colour, changes are applied.

What can I do ?

Thank you

P.S : Our website is under construction, I applied an exception on the contact page so you can see the menu

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