You have the right to contest the "Habitability Plan", though the time may have expired. You should contact the LAHD.
If the LAHD has registered the apartment building and there is no certificate of occupancy, you should contact the LAHD and ask why. They may have accepted approved building permits for habitable housing units in lieu of the Certificate of Occupancy.
If the building has no certificate of occupancy, you don't have to pay any rent and you can sue the landlord for disgorgement of previously paid rent as well.