As I can see, the value was not increased – https://prnt.sc/ur1xox Contact your hosting provider one more time.
Very likely you reached the Max Input Vars limit because of menu items number and your WP can’t save all the settings of your menu. So, if you choose the option, save the menu but then you’ll see that option is not saved then increase max input vars limit to 5000 or 8000. Read more http://sevenspark.com/wordpress/menu-item-limit
Regards