If you are blocked from entering your site, you can enter the IP or IPv6 address(es) via WordPress.com by visiting My Sites → Settings → Security → Whitelist.
You can also whitelist one IP address by setting it as the
JETPACK_IP_ADDRESS_OKconstant in your wp-config.php
You can find your IP by visiting any of the following sites:
Be sure to replace X.X.X.X with your own IP address.