His girlfriend got sick, so Abel went out to get food and get medicine. The phone that is ringing means he's coming, and he is in fact in front of her door.

When she isn't answering, much to his chargin, he sent a text that is right outside her front door, and he in fact knocking on her door. Basically, he said in the text, "Open the door, I'm outside."

It's a matter of Lili gathering the willpower to get up from bed and open the door.