Maybe you have got problem as I did with the temperature regulation of the 3D-printer. In my case I got this problem when I changed from PLA to ABS pro filament. When I set the nozzle temperature to what's needed for ABS it didn't stabilize enough. It oschilated around the set temperature and the 3D-printer refused to start printing.
It was the P.I.D. parameters that was wrong. After some research I found how to solve this problem. I have write it down how I did it. Maybe interesting for other users of 3D-printers.
http://www.astrofriend.eu/3d-printin...ter-setup.html
/Lars