Sims won’t go upstairs but house isn’t new

I’m on PC in Sims 4 and I’ve been playing in the same house I downloaded from the gallery since before I had 4 sim kids (so a long time) but suddenly now nobody can go upstairs. I haven’t changed decorations, moved furniture, nothings changed around the staircase. I tried rebuilding the staircase, taking off railings. I teleported them upstairs to sleep but now they won’t go back down on their own. Even when I say “go here” the bubble goes to queue and then immediately disappears. They don’t even react with the red X and footsteps.