NEC Multisync P402 Inverter not working

I have ordered and installed the the replacement Inverter and still the system is telling me the inverter is bad. The parts place sent me a replacement for the first replacement and still not working. 2 short and 1 long red blinking LED which NEC says something wrong with the inverter. I tested the DC volts going to the inverter on pin 1 and it has 23.9v dc the service manual say 24v dc so I think it should be okay. As I do PC repairs and only do LCD TV’s for for friends and business that know. Not sure what else I should look at that would cause this error code. I think I might need to look at the 12v dc and the 5v dc to make sure they are working okay. Any Idea’s please let me know and great thanks.