You seem to have a piezo transducer, not a buzzer. It need push-pull drive (transistor pulls down, resistor pulls up) as its effectively
a capacitor (perhaps about 30nF - this suggests a 330 ohm or so, less than this and you'll need a power resistor, larger and you might lose
high-frequencies).
Piezo transducers are highly acoustically resonant devices and you get the loudest output at the right frequency - so
try various frequencies. 12V drive ought to get a reasonable level I think.
Other ways to drive are put it in series with 150 ohm resistor and then drive from two pins driven anti-phase - this gives 10V peak-peak
signal without needing transistor or 12V supply.