I'm guessing this is for a 2011 or 2012 model? Leafs from 2013 onwards went to foot-operated manual parking brakes (a curious reversal of the trend).
Once you put a new 12 volt battery in, did it start working again? If not, there are videos on YouTube on how to manually release an electric parking brake, though I couldn't find one specific to Leafs or even Nissans in general.
Blue Ocean 2012 Leaf SV, lost that 1st bar at 34 months/26,435 miles. Lease returned 2 months later. Final LeafStat figures: 225 Gids, 17.44 kWH, SOC 91.89%, SOH 82.36%, 69.49% HX, 54.57 Ahr, battery temp 61.8 F.
Now driving a 2015 VW eGolf SEL.