When trying to create a graph in Apollo Studio, I'm getting the error: "We couldn't connect to that URL.". But my endpoint is correct

[gkpo]

When trying to create a graph i instantly get this error:

We couldn’t connect to that URL. Please double-check that it’s correct.

This is my endpoint URL: https://trotty-server-dev.fly.dev

What could I be doing wrong ? I’ve tried adding Apollo-Require-Preflight header as well but no success.

Thanks in advance for your help!