No target endpoints found for integration

Hi. I got the same error too. Did you include both the IPv4 address and Port in the Standard attributes for the service instances?
I got the error at first when I register the ip address only. It seems that API Gateway need both attributes.

The registered resources' attributes must include IP addresses and ports.
From https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-private.html#http-api-develop-integrations-private-Cloud-Map

Thanks, that link helped me. I'd registered my service in Service Discovery with an A record, but not a SRV record. I added an SRV record and it moved things on from 'No target endpoints found...'. (I now get 503 Service unavailable, but it's progress :-)

This worked for me as well. I was trying to setup my cluster in ECS using fargate. The service connect was working fine but requests were not reaching the services via http api gateway. After I added SRV records along with A records, both the connectivities started working fine. Thanks.