This looks like there is no preflight OPTIONS request, or an incorrect one, from that API. Is that a Snowplow Collector you’re sending the events to? Something looks up with the configuration, perhaps a load balancer or collector configuration issue.
I’d check the response of the OPTIONS request your browser is receiving. It looks like something isn’t configured correctly, either your collector configuration or any load balancers that you have in front of the collector, so your browser blocks the POST request.