Black screen on install test (but LED's!)

Just replaced my 4500 with the 5600.
Power was expanded to the two main power and two master gnd connections. I backup battery was also installed.
When applying power the Ethernet jack led's blink but the screen never comes up.
With only the backup battery, the Ethernet jack LED's blink while the button is being held down.

Ia there any reason the main screen would not come up if just the backup battery was connected? I tried the 40 second screen reboot but nothing happened.

Try it with only the backup power connector to make sure you don't have a wiring problem.

One led should be solid and one blinking, also make sure you are not trying it on a dead battery.

Pulled out and connected only the bu batt. LEDs, one solid one blinking while holding btn 1 down. Still a black screen.. also tried a second battery