We recently made a change to improve our platform. As of today, all newly configured receivers will be required to use HTTPs (SSL/TLS). Currently active Scanning API and Webhook receivers have until August 20, 2019 to upgrade receiver configurations to HTTPS (SSL/TLS), after which time non-HTTPs receivers will be disabled. Steps to configure a secure receiver can be found in the Developer Hub (linked below)!
To learn more about these changes - please check out this Security information in the Developer Hub, or the Announcements tab in the dashboard. Any affected HTTP receivers will be listed in this section to make it easier to find and remediate them.
Documentation for Scanning API
Documentation for Webhooks API