SparkFun EL Sequencer does not work
It looks like Sparkfun probably only put the bootloader on the board. The tutorial is written in a way that suggests the need to flash the board.

Also the board does not imediatly work with the 12V inverter. If you have the battery you should attach it and see the PWR LED turn on.

The inverter only provides voltage to the EL wire and not the Microcontroller, power to the microcontroller is provided by way of a regulator(U2), not the LM317 the last quote from the one comment shows how you can connect to the 12V inverter.

What you should do instead of having to go the route of all the wiring is to connect both the battery to BATT IN and the inverter, but ensuring that the microcontroller is programmed before hand.


  Arduino Code
  
  Once you have all of your hardware hooked up properly, it’s time to
  program your Sequencer to run the EL Wire display as you want. You
  will need to download the Arduino code in order to follow along with
  the example.
  
  You can also download the most up-to-date code from the EL Sequencer
  GitHub repository.
  
  We will be working with the “SparkFun_EL_Example.ino” example. If you
  need a review on how to upload Arduino code to your board or using the
  Arduino IDE, please check our tutorial here. Also, if you are unsure
  about installing the FTDI drivers, please check out this tutorial.


Also from one of the Tech support notes:


  Using 12V to Power Both the EL Inverter &amp; Microcontroller
  
  If you are using a 12V wall adapter to power the 12V Inverter, you
  would still need to provide power to the microcontroller side. One
  solution with your 12V wall adapter to provide power to the 12V
  inverter and Atmega328P is to get a barrel jack adapter to 2 pin JST
  adapter [ https://www.sparkfun.com/products/8734 ], thus connecting
  the 12V wall adapter to the “BATT IN.” This is assuming that your wall
  adapter is using a center positive barrel jack.
  
  From there you can connect the 2 pin JST labeled “DC Out” to the 12V
  inverter’s input voltage. To connect, I recommend using the male DC
  barrel jack adapter [ https://www.sparkfun.com/products/10287 ] and a
  2pin JSt jumper wire [ https://www.sparkfun.com/products/8670 or
  https://www.sparkfun.com/products/8671 ]. You will need to wire strip
  the cable to be able to connect it to the screw terminals.
  
  Lastly, you would need to add a solder jumper to SJ1 so that you
  bypass the voltage regulator between your external power (“BATT IN”)
  to provide power to the inverter’s “DC OUT”. This will provide power
  to your 12V inverter’s input.


Warning: if SJ1 is closed, inverter will see 5V with FTDI plugged in and switch at USB