Do you have at least 400 food? Your villagers will have no interest in breeding until you have that much stockpiled -- they might go indoors, but more likely that they'll tell you they're not interested because they're hungry.

It will also take a while because (I'm guessing) you have Level 1 Fertility. It might take 15 or 20 tries to have a successful mating at that tech level.

To save yourself time, pick the female you wish to have a baby, and set her preferred skill to breed. Once she's a Trainee Parent, she will keep trying even if you have the game off.