For Visa Developer error codes, go here - https://developer.visa.com/pages/visa-developer-error-codes
The project is trying to hit an URI/http method combination that does not exist.
Refer to the API documentation to validate you are hitting the right endpoint.
To further investigate, please provide the following information:
1. End Point
2. Request Header
3. Request Body
4. Response Header (include the x-correlation-id)
5. Response Body
Using SoapUI, you can find the x-correlation-id in the Raw Tab of the response header.
Is your Method Not Allowed issue resolved?
405 Method Not Allowed response status code usually means you either tried a GET on something that only allows POST, or vice-versa, or tried http: on a method that requires https.
same here that URL(https://sandbox.api.visa.com/vdp/helloworld) takes Get Method and you're using POST method while making a request.
in order to correct that error change your request method to GET