Motors not working in ramp 1.6 marlin 1.1.x

[ammarfarsi]

hello.
I use marlin 1.1.9 on ramps 1.6 but the problem the motors not working. I check the connection but it is correct. also, I use Vref for a driver I try 0.3, 0.42, 0.52, 0.72 , 0.93V but still motors not working. I use pronterface to check the printer is connected but motors not move. i work with A4988 driver
Marlin-bugfix-1.1.xmmm.zip