I searched through the forums, and was not able to find anyone with this issue, so here we go:

I created a new university neighborhood the other day, and was going to start with a secret society lot. In the past, I have had no issue going into a new University neighbourhood and making a secret society lot, and then rezoning it to secret society. This time, I placed a downloaded lot into the University neighbourhood first, and went into the lot to change the pre-existing dorm doors to a normal door, and made sure that the kitchen equipment was not the equipment used by the cafeteria NPC. I saved the lot, then went back into buy mode and used the cheat to rezone the lot to secret society (changeLotZoning secretsociety). I then saved and exited to the neighbourhood, but the lot was still visible, and it had turned into a rent lot. I went back in and tried the code again, but nothing changed after saving.

I then decided to try and make and re-zone a greek house. Again, it would only show up as a rent lot. I decided to try a new university map, and tried to do the secret society lot again a few times, to no avail. I then started a new university neighbourhood (again) and made a secret society lot from scratch, and saved (it was designed as a community lot) then tried to re-zone it to secret society, saved, and exited, and then went to neighbourhood screen, again to find that it had been changed to a rent lot again.

There are no other lots in these neighbourhoods, and I have been able to zone secret society lots in the past before, and have not added any new custom content since the last time I re-zoned a lot. I have all of the expansion packs, and the luxury stuff pack. Hopefully someone has heard of this issue before, or have any ideas.

Thank you in advance for any help!

After rezoning the lot as Secret Society, you need to move it to the lot bin, then re-place it in the neighborhood. Then it will disappear.

wow, I feel like a right idiot. But thank you so much for your help - alas, it worked!
I am going to assume that it works for the greek lots too. Thank you so much again!