[SOLVED]
Act 3:
She won't show up in [spoiler]the Arcade[/spoiler], and I think McCoy has to talk to her to be able to progress [spoiler](be able to talk to Sebastian again).[/spoiler]
Thanks!

edit: spoiler tags not working?!

Sometimes you have to revisit the arcade few times if you wasn't lucky to spot her there.

Hint: you don't have to leave Hysteria Hall (location) - just walk into the arcade few times and you will see her for sure.

Thanks, did that a dozen times without success!
I think I had to follow other clues before; now she's there.
Cheers!

I had the same problem and I was nearly giving up. Starting the game from last save the next day fixed it miraculously! :-) Played the game through already. Its fun!

I'm playing Blade Runner Enhanced Edition and i'm beginning to think there is a bug in game that prevents going further.

And I have tried many many times, entering out and in hysteria hall's entry and sleeping and travelling to places and entering hall after that, but lucy is not there, walkthroughs don't give anything to resolve this.

I' have arrested Gordo on night club row but that should not matter?

I even tried reloading game from act 3 start (before gordo arrest) and cheked hysteria hall but no lucy.

It could be a bug, but it could also be the specific scenario your game is following due to the arrangement of who is a Replicant and who isn't.

So, if it's as I suspect, first a hint:
[spoiler]
- You should go to the other night club in Night Club Row and deal with the situation there first. And only after that, try again to find Lucy.[/spoiler]

Edit: Sorry, it seems that spoiler tags have stopped working on GOG forums (?) So I'm deleting the rest of my post and will divulge any additional info (with more technical details and unavoidably spoilers) on this only upon explicit request.

Thanks for your help!
I went to nightclub and found Early Q in VIP bar (don't know how i didn't notice him before, when i was there multiple times)
and talked to Dektora and did the test
and now Lucy is standing in hysteria hall :)