1. Hold down battery button for 10-15 seconds
2. Try all 3 ports of 3-port DJI hub
3. Try charging battery with micro-USB cable while it’s in the Spark (This one most likely to work). Try holding down button again while inside Spark
4. Try different wall outlets (a long shot)
My Mavic battery had that light pattern on day 1 and it was DOA. Other folks have had success with Spark battery by charging it while inside the aircraft with cable.