Batteries won't respond to system

Always be sure the battery is charged and suited for your camera.
Check contacts of the battery and in the battery compartment of your camera. Dirty or oxidised contacts can be cleaned with a dry cloth. Never use sharp tools to clean contacts or anything in or on your camera.
Always charge the battery before using it for the first time, or if you have not used it for a long period. 3 months is a very long period.
Also check if the battery door is closed correct. Most cameras do have a switch connected to the battery door. If the switch does not work correct, it could be you can't switch on your camera.
If you have a multi meter, you can check your battery. After charging the voltage should be higher (few tenths of a volt) than the voltage printed on the battery.
If the voltage is slightly lower, you know thee will be not enough left when the battery needs to deliver some power.
Do not use alkaline batteries unless it is absolutely necessary. In some cases, alkaline batteries may have a shorter service life than NiMH. Alkaline battery performance is limited, especially at low temperatures. The use of NiMH batteries is recommended.
Never use manganese (Zinc-Carbon) batteries in your camera.