Two requests that prove your setup works. Send them in order.The first needs no credentials at all, so it tells you whether base_url is correct. The second is a fully signed request, so it tells you whether api_key, api_secret and origin are correct. Testing them separately means a failure points at one cause instead of four.
Your base_url is wrong, or you cannot reach the host. Check the address supplied with your account, and check it starts with https:// and has no trailing slash.