Need fuel air spark compression. Check that injector is firing, for mechanical or electrical failure. Check coil on plug/wire if loose or damaged. Check spark plug, just because it’s new doesn’t mean it’s exempt from manufacturing defects, damage/wrong gap from transport, or improper install. Dielectric grease or antiseize in excess or the wrong places will cause misfires. Lastly compression, make sure that cylinder’s compression is similar compared to non-missing cylinders.