Is this right?

[SIMone de beauvoir]

Hello,

I can't build on apartment lots, not even when they are empty. Is this right?

There's an option in the InSIMenator that should allow me to build, but it's not working for me either.

Help, please?

[Michele]

Correct.
Best method is to back up the empty apartment building, then "changelotzoning residential", save and exit, re enter to build, and stick to the rules for apartment building.
"changelotzoning apartmentbase" when done.
If built right, it should throw no errors.