no response for API calls from specific IP address

[Art Wu]

Since 2+ weeks ago, all calls made by a client to the eventbriteapi.com/v3/events/search endpoint from 54.235.159.202 (Amazon Web Service) timeout. Calls made from the same client running from a non-AWS IP address complete successfully. How do I get this range of IP addresses (US region) unblocked - https://support.appharbor.com/kb/tips-and-tricks/application-server-ips-ec2-configuration?

Thanks,
Art