my sim wont walk up the stairs and into the house

i just created a new house on elevated terrain. i made stairs leading up the door in a somewhat L shape. the same shape is on the back door, and my sim seems to be fine walking through the back door, but not the front. I've replaced the door, debugged my sim, traveled and came back, exited the game and came back in, changed stair shape, and changed terrain, but literally, nothing works. my sim refuses to walk up the stairs and into the door. I've added and removed the railing but it makes no difference. does anyone know how to fix this?