When you replaced the battery, did you power down the mains before replacing. This is important for this panel and I think it has self resetting fuses rather than replaceable IIRC.
So take off the battery then the mains and give it 30 seconds and then PUT THE BATTERY ON, then enter your code and then turn on the mains.
This should bring it all back up.
This panel is pretty hard to destroy.
Alarm
December 2012