Okay, so I have an interesting issue.

I moved a family into an apartment of a world I downloaded and they're not able to enter their unit. I can see inside, and go into build/buy mode to do what I like, but the sims can only ring the doorbell, and then and NPC comes out to greet them. The door across the hallway, leading to a black empty room is 'their' door. I get the interaction for locking it, but the sims are not able to go through it.

I'm not familiar with building and setting up apartments, but I'd like to fix this issue. What do I need to do in order to gain them access to the right apartment? I'm sure this is a marker issue, but I'm just not familiar enough with the markers to go clicking them and changing things.

I went through and did so much tedious things that didn't work before you commented, lol. I didn't think to just switch the doors. I thought it was an issue with the markers. Wow... thank you!

I see, and yes, that was the issue. Before you commented I was moving the family out, going into build/buy mode and replacing markers, double checking markers... and doing this multiple times. Now I know what to do if I run across this issue next time.