You should ask author of multilanguage plugin.
Also you can have cache issue. Deactivate temporarily multilanguage and cache and check
I have selected one menu and set it as Main menu but in Manage location option it is always selected to Live menu.Why it is not saving.
Link on page with issue (Optional): https://dev3.zotezo.com/wp-admin/nav-menus.php?action=edit&menu=33