Unable to login on subsites with mapped domains

I’m in the process of consolidating two of my standalone WordPress installs into an existing WordPress Multisite of mine.

I was able to create the new sites and change their respective sub-domain URLs to the new domain names and updated my DNS to point at the root of the network. Loading the new sites works as to be excepted however I’m unable to login to the dashboard over either of the new sites.

I tried adding the below code from this link https://wordpress.org/support/topic/error-cookies-are-blocked-or-not-supported-by-your-browser-1?replies=18 to the wp-config file but logins wouldn’t carry from the main site to the two new sites. The issue only seems to happen with the new domain network sites and not my other sub-domain network sites

define('ADMIN_COOKIE_PATH', '/');
define('COOKIE_DOMAIN', '');
define('COOKIEPATH', '');
define('SITECOOKIEPATH', '');