One of my clients is experiencing an issue when trying to upload an attachment to one of his Deals. I was able to reproduce by uploading a simple text file to a Task object in the test account available to me. The error that we are encountering is the below:

[INVALID_REQUEST_METHOD] The http request method type is not a valid one.

What makes this confusing is that the documentation for the pertinent endpoint indicates that POST is the appropriate HTTP method for the request ("https://www.zoho.com/crm/developer/docs/api/upload-attachment.html"), which is our application is using for its HTTP request. The full details of both the HTTP request from our application and the HTTP response from Zoho CRM (as captured in Fiddler) are recorded in the attached file. Would you have an idea about which part of our request would contribute to this error response?