HTTP 501 Not Implemented means the server does not recognize or support the HTTP method used in the request. This is different from 405 Method Not Allowed — 501 means the server does not support the method at all, while 405 means the method is not allowed for that specific resource.
The server received a request with an HTTP method it does not implement (e.g., PATCH on a server that only supports GET and POST).
The endpoint exists but the functionality behind it has not been built yet.
Try using GET or POST instead of the method that caused the error.
Send an OPTIONS request to discover which methods the server supports.
curl -X OPTIONS -v https://example.com/api/resource