They can enter, but aren't strong enough to break down a door.
The creatures don't seem able to pass through barriers, like doors or barred windows. However, in the novel, they enter open rooms and houses.
Malorie takes a dog while searching a bar/nightclub in the neighborhood for audio equipment. While Malorie searches the bar blindfolded, one of the creatures is inside and she hears the dog go insane.
The movie depicts the creatures quite differently.
A creature is inside the room with Malorie and Olympia when they're giving birth. That's when Olympia see it, not like in the film where she sees it from outside the window. The film did some REALLY stupid stuff with the creatures. They don't shake trees, make leaves levitate or appear to you as your worst fear or dead loved one. They don't speak to you in voices either. They seem to just... exist. It's almost as if they don't even know what their effect is. They don't open doors but will go through open doors, though. They don't even seem actively malicious. A creature almost takes Malorie's blindfold off when she's on the river. It pulls the blindfold from her face and she puts her hands on the blindfold and says, "This is mine" and after a tense moment, the creature leaves.
In the movie, the creatures have this presence and seem to control wind. Hence cars shaking, leaves flying, hairs raising, etc. That is not enough to break down a house door.
Disclaimer: I haven't read the novel, I'm quoting comments from here.