@kreativeangel93 Sorry for your trouble. I will suggest a few things that have helped me get past some similar dynamics.
Firstly, you said you had Mods/CC but have removed them. A couple of things you should do after removing them is:
Once that is done please restart your game again.
Now go into your lot. Even if the issue is gone for future purposes your roof and floor will likely need to be re-added. Please go to the first/ground floor and....
- Re-trace the room all as one with the 'tracing' (first one on the left) wall tool. Sometimes when you do this once you get all the way to where you began the room re-builds itself. I have noticed that this 'tracing' technique has not been working for me lately, though it used to, so I am not sure if it is the situations I used it in or a change in the game's behavior. Anyway, you can try this first. If that does not re-create the floor and roof...
- Please try using the square tool and re-create the areas. Each time you stop dragging the square tool it should automatically create the ceiling and floor to that area. Once you have done that in a way that re-created all of the space you had originally to make the building outline you had that all has flooring and ceiling, go up a floor to confirm you are seeing the ceiling too then go back to the ground floor-first floor and draw/delete all inner walls that you do/don't want.
- Another thing that you can sometimes do on a room is click the wall to highlight the room (sometimes I need to do this more than once or in different areas or by going to the nest floor up/down in fussy situations) until you get either the yellow inner-rim coloring that when hovered over gives the option 'build ceiling'. click on that yellow area to build the ceiling in that room/area that is highlighted. Similarly in some rooms/areas you will have times that it will give you the option (not yellow in this case) to 'build floor'.
Please let me know if these things do or do not work. If they do not We can try a few more things. Thanks!