was printing fine... now When i hit print the printer is unresponsive

I had my printer successfully printing for 3 days but now after I hit the start print button nothing happens. before I hit start print I am able to manually control it but after it becomes unresponsive. it usually raises up 5mm or whatever I have it set to butit isn't. it shows that it moved up5 mm but the motors don't move. the extruder heats upas normal but theprint job never actually starts. I already ran pid autotune but it didn't correct it...please help