Really excited for the new content - I installed the latest update and finished each of the 4 individual routes, but I'm not seeing New Game Plus unlock. Maybe I'm missing something?
I'm having exactly the same issue, and I just finished the PS4 version an hour ago. I have good endings for all four routes - all show checkmarks - and I just can't get New Game Plus to show up. Nothing has changed on the Extras menu, and "New Game" just starts a regular new game.
The only thing I'm missing are a few CGs, but from everything I've read you don't need to unlock them all for NG+.
Edit: I can confirm that doing Julian's route last was the issue, and that replaying another route unlocked NG+. Thanks for reaching out on Reddit for the help!
After every playthrough, there are scenes after the credits. Make sure you watch these all the way through until you get a message about a new path unlocking.
I think there may be a minor bug happening if you already completed all the routes before the new update, OR if you play Julian's path last. If my theory is correct, replay Maddy's, Liam's, or August's post-credits ending sequences until you get the New Story + Unlock message. Let me know if that fixes it. I'll also work on a patch to make this update smoother for those who experienced this.