Sims 4

Is there something upstairs that is blocking the way?

If there isn't I once had this happen to me. I went into build mode and moved the stairs a bit and that seemed to fix it? 

I tried that too and it still didn't work. I even moved my sims to another house and it was doing the same thing.

@Lisa7958 Please check this Bug Report to see if it matches your issue. If it does please add your 'Me Too' to the report and subscribe in order to receive updates when a fix is in place. In the meantime check the second comment on the bug report for a list of workarounds that have been found: https://answers.ea.com/t5/Bug-Reports/WORKAROUND-Open-staircase-cause-routing-failures/m-p/9716427/highlight/true#M160338

Hi Hopefully, you already got this issue figured out but I would like to respond so people can know how I dealt with the problem. When I saw the exclamation mark and footsteps in a thought bubble I was concerned and I didn't understand what I should do until I stumbled across this website. I had downloaded a lot in the gallery and the upstairs became inaccessible so I deleted the top floor and the stairs and once I did that there were stairs already under the ones I deleted so the stairs became accessible again. 

Some other tips are to make sure the staircase is not blocked and If It looks clear I would recommend starting a new lot and trying building a new lot. If you are using bb.moveobbjects or download a lot from the gallery sometimes the game does not register the cheat and it makes the stair inaccessible. 

Another tip is if you have too many mods in your Sims 4 then put all the mods in a different folder and restart the game then put all the mods back in and it should go back to normal. The game Sims 4 is not perfect but it can be fun with the right amount of knowledge of overcoming these reoccurring issues. 

Please don't be afraid to reach out for help if you are still having issues or the information I gave was wrong in any shape or form. We are all a part of the Sims community therefore we should express our concerns in these games. Thank you so much and I hope this information helped you as it helped me.