connecting teensy + A4988 carrier + motor
From the photos it appears that you are trying to drive a DC brushed motor (2-wires) using a stepper motor driver chip/breakout.  This could maybe work in a limited way if you hooked up the two motor leads to one of the phase outputs (e.g. 1A and 1B), but pulsing the step input line will not work the way you expect.  You will get a constant current from the one phase if it is enabled but no current when it tries to drive the other phase (that does not exist). In short, either get a stepper or drive your DC brushed motor with an appropriate driver chip (H-bridge with some control input).