The HTTP 451 Unavailable For Legal Reasons is an error status code of the HTTP protocol to be displayed when the user requests a resource that cannot be served for legal reasons, such as a website that cannot be displayed due to privacy laws. The website owner will typically force this status code.
Browser console and TCF
The browser console error:
Failed to load resource: the server responded with a status of 451 ()
when using Transparency and Consent Framework (TCF) signifies a vendor has blocked their resources to be loaded, due to privacy law limitations in your specific region, or when the vendor can’t comply with settings provided by the user’s consent. These errors won’t cause issues on the front-end most of the time because the vendors related to these errors won’t serve advertising products, but merely collect data. And in the case of an error, they cannot.