Okay I fixed it! Turns out the save was corrupted because I moved with any animal at all. Just had to go back to the save before I moved, sell all the animals and then go on.
So apparently when you own animals (I, for example, had six chickens, a llama and a cow) and move to a different lot, your save file gets corrupted. Fun! I wanted to move to a larger lot with my generations save because my sim had a set of twins with another on the way and I'd been dealing with a 30x20 for far too long. Did so, spent a few hours making a huge farm I was very proud of, and when I moved my sims onto the lot it. Didn't work. I couldn't enter the house or even see into it. The page-down and page-up buttons didn't work, and I couldn't change the walls. So then I spent three hours preparing my game, factory resetting, etc until I found out that somehow my save had been corrupted. I've fixed it by going to a save from before moving and selling the animals so I don't move with them this time, but it sure isn't going to bring back the hours I spent on that house.
