Domain doesn't change to active after changing the MX record to Symantec.
Message of "Update now" can be visible on Email Security.cloud.
1. There is another MX record besides MX records of Symantec.
1. Delete other MX records, and make sure only the MX records of Symantec are registered.
2. Contact the support team If the "Update Now" still exists after the 24-48 hours of propagation.