Quoted from Groo:I don't think we've played well enough to earn an extra ball yet and haven't been notified that it is lit, but the insert is lit up quite often. I'll take the glass off and try it tonight.
Try the led test and see if it the extra ball insert is hooked up correctly. The led may be swapped with one for the GI if it is on quite a bit. This happened on my ACNC with the hurry up target and took a few weeks of playing to figure out.