My hitachi nailer wont fire

Start with the basics:
First check that the butane (or whatever gas is used) canister is full. If empty, put in a new one.

Second check to make sure your battery is fully charged to be able to fire the spark to work the nail gun. If not get the battery charged and/or replaced as needed.

Third make sure all of the safeties are working properly and that you have them engaged to the piece of wood you are nailing when you try the trigger.

If beyond that it does not work it could be a bad trigger, a bad safety switch, or even a bad connection from the battery to the device.