Unable to Move to a Section of a Room/Home

I made a brand new home on a lot after bulldozing a different home/lot. I put in stairs to go from the first floor to the basement and to the second floor.  There is a section of the floor in front of the stairs that does not respond when I click on it to move my sims there.  The sims are unable to go to the second floor or the basement because they cannot go into that section of the first floor great-room (they do the emote with the red exclamation mark and the feet).  Restarting the game did nothing. Taking down the stair railings did not fix the issue. Taking the stairs out did not fix the issue either (the area is still unresponsive when I click on it).  I looked at both the basement under the area and the second floor over it, clearing them out of all items, but that did not work either.  I attempted building a new room in the area and added an arch to see if they would walk through it, but that did not help.  I attempted looking at the area through different windows to look for items in the way, but saw nothing.  I also attempted changing the height of the walls but still nothing.  So far, I have identified 14 squares on build mode that are not responsive (I made them white concrete on the picture attached).  I do not use mods of any kind, just the regular game cheat codes to move objects, make them bigger/smaller, etc.  Any ideas on how to solve this issue?  I really like my Gnome House and would hate to have to give up on it.