I\'m testing to make mobile game server with AWS\'s Lambda and API gateway. At the API gateway, I try to make custom domain using 2 types endpoint, regional a.domain.com
a.domain.com
I had the same issue.
It appears that when using API Gateway with regional custom domains only HTTPS is supported and API Gateway does not redirect from HTTP to HTTPS.
So just use https://a.domain.com
https://a.domain.com