504 Time-out when calling POST Create App User

I'm having a problem with using cURL to create an app user. I'm passing a valid name and toggling is_platform_access_only to true and using my developer token as the ACCESS_TOKEN yet I cannot seem to get a non 504 response from the server. When I use the Try It Now demo in the reference page it gives me a 403 access denied insufficient permissions error.

When attempting to post a support ticket the "Submit" button let me delete the text "Submit" and write whatever I pleased but it didn't function as an actual submit button... so I'm asking here

If anyone could help that would be fantastic. Thank you in advance.