My lots aren't loading

I was playing in one household for a while, but I decided to make a new family to move in next door. After creating them in CAS I moved them into a lot from map-mode and started building the lot from there. I did not go into live-play with the sims as yet.

I built the house to my satisfaction, but when I entered live-mode to get the family settled, the walls were up, as if we were visiting a lot. I tried to put them down, but it didn't work, I also tried to move down a layer as I thought it had loaded on the roof, but when I clicked the button it went gray as to show you cant go further, but the 'go up' button was also gray, so I couldn't go up either. My sims could only interact with the outside of their house. 

This had happened before when I accidentally moved my elderly couple into a rental lot and when I took their grandchildren to visit all the furniture was gone, and when I opened build-mode, it only loaded for a few seconds before transitioning back to live-mode. I was not sure what to do with it, but since it did not affect them much, i simply moved them out of the world and continued on, avoiding the lot.

What caused this and how do I fix it?!

I didn't go back to my main family lot in fear of experiencing the same thing.