The sense of circular polarization of the fluorescence from dyes dissolved in chiral nematic liquid crystals (CNLCs) with a photonic stopband overlapping the dye emission ('resonance regime') displays a peculiar reversal as a function of wavelength, which so far is not satisfactorily explained. We systematically study this phenomenon and show that theories based on the guest/host alignment of the fluorescent dye in the CNLC matrix are not adequate in the resonance regime. We instead propose a consistent explanation of sign reversal based on the description of CNLCs as one-dimensional (1D) photonic crystals.