You tested something completely different that what I suggested, and only demonstrated that your server was functioning correctly.
The error you received was:
{"errors":["param is missing or the value is empty: nonce"]}
The server is correct. You called this API incorrectly, hence the error. You’ll get the same result against e.g. meta.discourse.org:
○ → curl https://meta.discourse.org/user-api-key/new
{"errors":["param is missing or the value is empty: nonce"]}