Hi Steve,
Modem MSE (dB) The MSE (Mean Square Error) of the RX signal, measured in dB
This should be between -30 to -40 for a good working install in my understanding. Most of my links are around -35dB. -99dB means the modem is not talking to the far end, less than -30dB to me says your RX power is to high.
LinkPlanner should show you your expected receive power and voltage, and what to set your TX power to. Was you link comissioned on this?