First Clear Browser Cache (including cookies) + server cache from cache plugins etc. Then set the following in your wp-config.php file: define(‘ADMIN_COOKIE_PATH’, “https://wordpress.stackexchange.com/”); define(‘COOKIE_DOMAIN’, ”); define(‘COOKIEPATH’, ”); define(‘SITECOOKIEPATH’, ”); Also, you may checkout the answer from HERE: define(‘WP_ALLOW_MULTISITE’, true); define(‘MULTISITE’, true); define(‘SUBDOMAIN_INSTALL’, false); define(‘DOMAIN_CURRENT_SITE’, ‘your-domain.com’); define(‘PATH_CURRENT_SITE’, “https://wordpress.stackexchange.com/”); define(‘SITE_ID_CURRENT_SITE’, 1); define(‘BLOG_ID_CURRENT_SITE’, 1); define(‘SUNRISE’, ‘on’); If it … Read more