You are probably exceeding the maximum speed of your motor. 200ms per revolution works out to be 300RPM. The A4988 library recommends no more than 200RPM.
When I tried your code, my stepper didn't even rotate until I increased the delay.
You are probably exceeding the maximum speed of your motor. 200ms per revolution works out to be 300RPM. The A4988 library recommends no more than 200RPM.
When I tried your code, my stepper didn't even rotate until I increased the delay.