signifyd.com API empty response?

Question

PHP

I'm trying to connect signifyd API to the store.
On their website, the console says {"message": "Provided API Key not found."} even if you change the default one to mine.
The JS console on the local server says No 'Access-Control-Allow-Origin' header is present on the requested resource.
And in response Access-Control-Allow-Origin comes empty.
If someone has come across this, tell me CHADNT?
PS: in the API description there is a line Be sure all API calls to SIGNIFYD are made over HTTPS. Otherwise they will fail. Does this mean that my test site should have a working https with SSL or just write the address with https in the request?