When a Sandbox is created from a copy of Production, the integrations are disabled by default to prevent accidental use of production services; it's a great error as it gives you a chance to point integrations to a Sandbox or turn them off. When that message pops up, it does not indicate what extension was trying to reach production services.

To troubleshoot that issue, you have to guess what extension could be blocking the request by enabling Https services for the extension, but if you have several services like that, it's not easy to find the extension blocking the request.

Add "Extension XXXX has blocked the request to prevent accidental use of production services." -- This should point you to the correct extension and will save you 2-15 minutes trying to find the correct one.