She can't be level 5 love - level 4 is the maximum right now. If any girl is at level 5 for you then the game's variables have been edited and that will break the game in a wide variety of ways.
The system is working, so if a girl isn't getting pregnant then it's definitely for one of the three reasons I mentioned. Bear in mind that babies in the day care also count and will prevent the mother getting pregnant.
Hate to bear more bad news but I'm having the same problem. Though I do have a touch more information to provide.
First, I started a new game from the start for the most recent update to avoid any save/load bugs between versions.
Lily, Kana, and Annie are all Love level 4. I have completed building the day care, and there are no children in it.
I had sex with Kana before the day care was complete, and she got pregnant. I got the cutscene to visit the Artifact and talk about how babies will work. The thing is, I don't even have access to the Nexus yet, and it's involved in the scene, so it creates some discontinuity there. (I also am having trouble getting access to the Nexus, the murder mystery seems to have blocked my ability to activate the event to get into it?)
Anyhow, Kana gave birth and there was talk about how she can't keep the baby because we have nowhere to raise it, baby goes to artifact.
Next, I completed Lily's story, love to level 4, had sex, get message (something is preventing...) assuming this is working as intended here.
Then I got the money to build the day care, which I did.
Now even though the day care is complete, when I have sex with Kana or Lily, I still get the (something is preventing...) message.
I just finished all of the love events for Annie, and had sex with her and the game surprisingly told me she got pregnant. But both Kana and Lily are still being prevented from getting pregnant.
Not related, but I also have the succubus lead problem. In fact, I got the succubus lead at the start of Act Two.
