Gum Ball on the door is NOT the gumball machine. Gum / Ball when lit together on the door enables 1 or multiple locks depending on difficulty level. Gum / ball on the door does NOT go back out until all ball locks have been locked (Basically both Gum and Ball being lit is the same as the lock light being lit.)

There is nothing wrong with the machine.

Each lighting on Gum / Ball on the door does add +1 to the count of Gumball machine enables. Which is shown by the shoot here for Gumball machine red lamp. This is a stacked count, but is NOT indicated by the GUM / BALL lamps on the door panel. Since this is the normal way to increase the count of Gumball Machine Enables, you do need to get gum /ball to go out on the door panel so that you can light them again; but again this is done by LOCKING a ball (or multiple if lock is set to easy or normal), NOT by shooting/hitting the gumball machine.

You must extinguish the lock light to get gum/ball lights on the door to go out, thus enabling another set of ramp shots and another increase to the shoot gumball machine counter.

This may take one/two/three/ locks or starting multiball depending on difficulty settings and current game progress.
A harder lock process means more gumball shots, but fewer multiballs, it's a setting trade off.

there are a number of settings that effect this in setup, number of shots until first lock, number until first multiball, held lock status, number of locks until second multiball, etc. 9.4 adds a number of configurations that 9.2 doesn't have to the configuration of the lock/multiball start/gum and ball lighting settings.

If the first lock is set to easy, then you have to start multiball to get the gum/ball lights to go out.