Unable to connect to tcp port

I have an app in docker, listening on port 12345/tcp. I verified locally that I can connect to it when I run it in docker and I publish the port. I have this fly.toml:

app = "my-app"

  internal_port = 12345
  protocol = "tcp"

    port = 12345

I can deploy it successfully, but then I can’t connect to it from my laptop:

$ telnet my-app.fly.dev 12345
Connected to my-app.fly.dev.
Escape character is '^]'.
Connection closed by foreign host.

(I replaced the actual name of the app with my-app.)

How can I investigate this?

This sounds similar to my issue, which turned out to be due to the recent release of shared IPs:

Thank you!