There are many posts/responses and such on this topic and not many work-arounds or fixes (many topics closed) so this will addresses this glaring issue many of us have with Wordpress not making new menus, provided the theme supports 2+ menus at once.
-Open .htaccess and add this to your first line:
"php_value max_input_vars 2000"
-Delete your menus and create a new one
-Copy the URL during the 'Create Menu'
-Make your menu
-Save the menu
-Paste the previous URL into the URL
-Change the number on the end:
(ex: http://mysiteDOTcom/wp-admin/nav-menus.php?action=edit&menu=7 When you create a new menu and save it, there will be a positive number like 3, 6, or even 7)
-After changing the LAST digit/number, and hitting enter in the url, set up a SECOND menu and save it with a different name.
-Go to Menu Locations and set your new menus.
-Save changes.
-Pat yourself on the back :)