This may relate to Cloudflare:
NOTE: Kraken has the "Browser Integrity Check" enabled.
This may occur if your request contains suspicious headers. For example, your request may be missing a user agent, or use a non-standard user agent; so please check your request headers.
If you're unable to create any standard requests that our system permits, send us a full copy of the request(s) that you're attempting, including your IP address and all headers. This information would allow us to investigate further.