API calls failing from one server but not another

I am making a simple call to the /api/v2/companies endpoint, using basic authentication. I use the API key as the username and “x” as the password, per the documetation.

On my machine, the call works fine and returns a list of all the companies.

On the live server, using the exact same credentials, the call fails with a 403 forbidden.

I suspect there is some sort of blacklist at the Freshdesk end, and there does not appear to be any place where I can inspect a request log to confirm or disprove that theory.

Can anyone help please?