max_input_vars not enforced in php.ini

It’s possible to increase it from .htaccess file in root WordPress installation’s directory. For this you need connect to your server via FTP (using some FTP client like FileZilla), find .htaccess file in the root of your site directory (or create it yourself if it’s missing) and add below lines of codes at the end of the .htaccess file:

php_value max_input_vars 2000

FTP login details is your cPanel login details. You can also use File Manager in cPanel to edit your .htaccess