Worker on custom subdomain does not load over HTTPS

I moved a worker to custom subdomain. It’s loading via HTTP, but not HTTPS.

I get this error from Chrome

Unsupported protocol: The client and server don’t support a common SSL protocol version or cipher suite.

The subdomain I’m using for the worker did not have any existing DNS records, so I setup a AAAA record pointing to 100:: as specified here: https://developers.cloudflare.com/workers/platform/routes#subdomains-must-have-a-dns-record

What is the route?

It’s data.somedomain.com/flags/*. This works, but HTTP only.

I’ve also tried https://data.somedomain.com/flags/*. This make HTTP not work, which is expected, but HTTPS still gives me the Unsupported protocol error.