NIB and auto-firing, that's cool!
The opto is located around the 'half moon' part, that rotates with the cannon.
There are 2 switches for the cannon as far as I know, both should be checked and might be adjusted in your case.
Great to see you're enjoying Pinside! Did you know Pinside is able to run thanks to donations from our visitors? Please donate to Pinside, support the site and get anext to your username to show for it! Donate to Pinside