If your domain displays a “This domain is parked” page the mostly likely reason is that the domain has expired. Less commonly the domain name may have been purposefully deleted.
You may renew a domain name which has expired by logging into your WordPress.com account and visiting https://wordpress.com/me/purchases.
Domains that have been purposefully canceled may be recovered, but cannot be guaranteed.
If you recently renewed your domain name you can check our guide on common domain troubleshooting steps to restore your domain.