Your relationship with Calypso was probably not high enough. For the past several updates there has been a hidden variable called `calypso_interest` in the code that gets updated based on your interactions with Calypso.I left when the portal first opened as there was no option to stay
It is basically the same thing as love points for the other girls except this is hidden - so no heartbeat, no indication that you made the wrong choices etc. She is basically a hidden love interest and the reveal that she is a main girl happens only during this update. So you wont even know where you lost her path because she's not in the main girls screen until 1/3rd your way through this update. I have not looked at the code yet but I'd be willing to bet that for you that hidden calypso_interest value was low and because it was low you were locked out of her scene.
You would have to replay earlier updates and make the correct choices.