I built my piper computer last night. We have looked at everything a couple times and it looks all good to me, but when I press the power button on the battery, the screen turns blue for 4 or 5 seconds, and then turns black again. A few seconds later the music comes on for about 30 seconds, and then it all goes silent again.
do you have a spare micro USB cable? If so use it to connect the pi to the battery. If t works, go to https://support.playpiper.com/hc/en-us/requests/new and explain what you did and request a new micro USB cable.