ES 450 won't power on

[mlandis]

I have an old ES 450 that's been sitting on a shelf for a while.  I just ordered and installed a new battery for it, but the unit won't power on.  A multimeter shows 12.9 volts on the battery.  Upon power-on, the green LED blinks a dozen times, then the unit clicks off. I'm thinking some internal POST is failing but there's not enough info for me to know what to do next.  Any thoughts?

[Teken]

Install the APC Power Chute (PCPE) software and connect the unit to the computer system. 

It should confirm what the active fault is / error code. In the interim let the unit continue charging the new battery for at least 24 hours.

Once 24 hours has passed remove the battery and confirm it’s at least 13.XX VDC. If the battery is still (Only) 12.90 VDC the unit is not operating correctly. 

Lastly, you may consider performing a brain dead reset.

Brain Dead: Disconnect all connected loads. Disconnect AC Mains from the wall outlet. Disconnect the battery cartridge. Press and hold the power button until you hear a click / beep.

You may not hear anything at all either! 

Reconnect everything including the USB cable for (PCPE) to the computer system -  except the attached loads.  

Power on the unit what happens?!?