none of the sims in my save can go up stairs

Hi, can someone please please PLEASE help me? I've messaged nearly every guru possible but no ones answered, which sucks.

I've been doing rags to riches game since seasons came out, and I've progressed quite a bit. 

I decided to build a second floor to my home as my sim was about to have a baby, but my sims cannot go up the staircase?

I've cleared all furniture, walls, windows, curtains, railings, and floors around them but they cant go up. when they complain the bubble has a staircase with a cross through it, im not sure if that's saying its inaccessible or the game thinks there isn't a staircase.

I've even built test staircases outside, clear of anything and my sim still refuses to go up. 

I jumped over into willow creek and started up the goth family, and they cant go up the stairs either, meaning they cant even get onto their porch to get into their house.

any help is really appreciated.

also, I would put this on the sims forums, but I haven't met the requirements to be able to post.