Dear
I am not familiar with Ubuntu. So in case of windows SMART PANEL/EASY PRINTER MANAGER can be down loaded from samsung web this will show the errors that the machine has.
Try to print a self (demo page) pressing stop s/w a while. If it works check the life of toner cart.
Thanks.
please install the smartpanel software from www.samsung.com. the program will read the error and displays on your computer. then you can take action on error displayed.