Right now the motor is in the "off" position and the speed looks to e dialed to minimum.
When you depress the red toggle switch does it illuminate ?
If you remove the belt from the machine, place the dial 1/2 way, and push the arm down, does it run?
There looks to be a fuse on the backside between the motor cord and the convenience receptacle. Logically, the red power toggle shouldn't illuminate, if the fuse is blown, but there's no telling how it's really wired.
One more source could be the brushes under those black plastic caps. They should be making contact with the armature via spring pressure,. If they're worn, the motor won't run. Generally it's intermittent though.
If it's not something simple, then you'll need a meter to see where you have power, or don't have power..
The speed controller on my Adler cannot be adjusted to minimum. There isn't enough torque available to turn the machine, so it just sits there doing nothing. Th speed dial on mine does not set an RPM, it just sets a range of RPM. My foot on the pedal still controls the speed of the motor and the needle.
To control the speed by setting a specific rpm, you'll need a speed set controller, and I don't see one in your photos. It should still work as it is though. Mine does.
One more silly possibility, and I did it to my self, is that the setscrews that tighten the pulley to the shaft, weren't tightened down, so the motor shaft was spinning inside the pulley. I felt pretty stupid when I figured that out.