What it means

A 501 Not Implemented response indicates the server does not recognize the request method or lacks the ability to fulfill it. Unlike a 405, the server does not support the method for any resource, not just the requested one.

Common causes

• An HTTP method like PATCH or PUT is not implemented by the server.
• The server is too old or limited to handle the request type.

How to fix it

• Use a supported HTTP method.
• If you are the server admin, implement the requested functionality or upgrade the server software.