LM339N - Comparator #4 not working as expected (always low)
Would you like to specify your desired threshold voltages and tolerances? 

This design is poor due to Zener Rs but could be improved with R9,11~14 raised to 10x...to draw less current.   Thus the R divider draws current from the Zener making its variation too much for your thresholds.

The best R values depends on your SPECS.

You can use whatever you want but you can see the threshold variation in the graphs due to the zener have improved. which caused your fault.  I would put the battery on Red alert below 14V.