stepper, either no turn, or no torque..

Hello,

I got a DRI0043 DF robot stepper controler and a 2A motor 57BYGH240-2,

https://french.alibaba.com/product-deta ... 70742.html

using the example code, I get high pitch noises, holding but not turning at all.
so I've changed the delays a bit higher to 500 microseconds...
now the motor will turn... but has no torque at all...
for this big one, it's impossible to has such low torque...

using my bench power supply 12v 4A, and
ON, ON OFF, (1 microstep)
On, OFF, OFF config (2amp)
tested the poles of the switches, they work.
double checked the shematic, seams okay.
even plugged on my scope... all 4 coils wire get their pulses...

I tried other libraries with no luck. any ideas why I get this ?