A developer has created an external calculator for me, with the intention of me passing a field data from Zoho via a webhook and the outcome of various calculations being returned in response.

I have created a function that creates a map of the various fields, invokes the URL and passes these as parameters.

The response I keep getting is:  "INVALID_URL_PATTERN"

If he posts exactly the same payload (taken from doing an info on the map) via postman, it works fine.

Does anyone know what might be causing this?