Cannot Access Admin Area After Migration

There is not enough information to pin point the redirection issue.

Here is what you can do to pin point the issue:

Check if your new url is somehow different from old url. If its
different then you will have to update your urls in database.
Check and compare PHP versions of your old and new environments.
Try to rename the active theme to temporarily disable it and then try
to access the admin.
Try to disable all plugins by renaming them and check if you can
access the admin panel.

Further more please check wp-config.php for following constants:

ADMIN_COOKIE_PATH
COOKIE_DOMAIN
COOKIEPATH
SITECOOKIEPATH

If the above mentioned constants are defined then check their paths else try adding following line in your wp-config.php

define(‘ADMIN_COOKIE_PATH’, ‘/’);
define(‘COOKIE_DOMAIN’, ”);
define(‘COOKIEPATH’, ”);
define(‘SITECOOKIEPATH’, ”);