If it's real old/been in the kitchen a long time the mech inside can get gummed up and just stop/jam. You either have to get a tech to take it apart and clean it or just replace it.
Turn it off, hold the feed button and turn it on, keep holding the button until it starts printing. After it finishes printing the stats, press the feed once and it will do a long red/black print test. If it conks out during this test it's probably gummed up inside or something else in there is failing and you need a service tech or replacement.
If it self-tests ok and it always prints full tickets then stops working and won't start printing the next one I'd be more inclined to look at the network if it's i.p. - bad switch port? Patch cords or network run? If it's IDN could be cable run to whatever WS is controller. Could be the i.p. or idn board in the unit also.