Background Request Blocked

After upgrading Cornerstone, I am receiving the following message:

Wordfence Firewall blocked a background request to Wordpress for the URL
http://mydomain.org/cornerstone-endpoint. If this occurred as a result of an
intentional action, you may consider whitelisting the request to allow it in the future.
WHITELIST THIS ACTION OR DISMISS

When I try to go to the above URL, I get:

What do I need to do to remove this message?

Thanks!

This looks like the same error [Http://2017.manchesteranimalshelter.org/cornerstone-endpoint]

Hi There,

As suggested, please whitelist the URL from your security. Please contact your hosting provider and see if they can disable the security or exclude that URL and all requests (all payload related to that URL ) from your security rules.

Please let us know how it goes.