Also try this please:

Also try to jump your car with a jump start battery or with another car or  with a battery charger capable jump start (50 A). If it can be started this way, it is your battery problem. 

Since 12.3 V of your car's battery is little bit low to start with, especially it is winter, try to charge your car's battery first with a battery charger and then start your car with newly charged battery, see if the engine can start to work.