has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

This error message usually occurs when a website or application is requesting resources from a different domain or server than the one it originated from. The browser enforces a security policy known as the "Same Origin Policy" to prevent malicious scripts from accessing resources from other domains without permission.

To fix this error, the server hosting the requested resource needs to include the "Access-Control-Allow-Origin" header in its response. This header specifies which domains are allowed to access the resource. If the header is not present or does not include the domain of the requesting website or application, the browser will block the request.

Web developers can also use techniques such as JSONP or CORS proxies to work around this error and access resources from other domains. However, these methods may introduce security risks and should be used with caution.