WordPress Multisite sometimes gets into a login loop with a reauth querystring parameter due wo domain mapping: “Error: Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress. ”
Solution 1 (Multisite):
Add this to your wp-config.php file:
define('COOKIE_DOMAIN', false);
Solution 2:
” I went into PhpMyAdmin > wp_usermeta > and deleted the meta_value for session_token. “
Solution 3:
It seems to be more frequent on multisite installations and on those it can take more steps. When the above fails, then adding the following lines to wp-config seems to work sometimes:
define(‘ADMIN_COOKIE_PATH’, ‘/’);
define(‘COOKIEPATH’, ”);
define(‘SITECOOKIEPATH’, ”);
There is a goodStackOverflow thread here: https://wordpress.stackexchange.com/questions/259839/cookies-in-multisite-where-network-sites-have-their-own-domain-name