You are trying to register your email domain to Symantec Integrated Cloud Connect Defense Manager (ICDm) so users can download the app from the Microsoft Store. When you put in your validation code/pin, you get an error message "Domain registration failed. Please verify that validation code is entered correctly."
This process is documented here: https://help.symantec.com/cs/saep/SAEP/v128981160_v123284638/Installing-the-Symantec-Endpoint-Cloud-Connect-Defense-client-on-Windows-10-devices-from-the-Microsoft-Store?locale=EN_US
This issue appears to be resolved on the cloud-backend as customers are now able to register their email domain.