[USR-TC] HiPER DSP NAC Cards Not being Picked Up

Hello, I've got a Total Control HiPER system (4 HiPER DSP modem sets, 2 HiPER ARCs and the NMC) Unfortunately, neither TCM nor the list chassis command in the HiPER ARC CLI can detect the back DSP cards. The cards do seem to be working, as the front cards show up in TCM and the span lights are lit, so the front card can see the back card. Anyone got any ideas?