Paper, the cover, power, the cutter, then the self-test — the order to check a quiet printer in, and how to read a blank or faded ticket.
A thermal printer that has gone quiet is not a counter that has stopped selling. An order rung in at the register is written down before anything is asked of a printer, and it stays written down until a ticket for it has come out of one. So nothing on this list is as urgent as it feels. Work down it in the order given: that is roughly how often each item turns out to be the cause.
A ticket that prints but cannot be read is a different fault from one that never arrives, and the pattern on the paper tells you which. Nothing at all on a ticket that fed the right length is almost always the roll in the wrong way round, or plain paper loaded where thermal should be. Faded evenly across the full width is the roll itself: thermal paper that has sat in sunlight, against a heater or beside a cleaning chemical goes grey and prints weak. The answer there is a fresh roll from a sealed box, not anything done to the printer.
A pale or missing vertical stripe is the print head, not the paper. Dust and sugar settle on it behind a bar, and a dry cloth sometimes brings the line back; if it does not, the head is worn and that body is near the end of its life. Half a ticket, cut through the middle of an order, means the printer lost power or lost its link mid-job - send that ticket again from the console and it will come out once, not twice.
Give the list one pass. If paper, cover, power, cutter and self-test have not brought it back, take the spare printer from the back, stand it where the dead one stood, and carry on serving. A working station is worth more than a repair, and the faulty body is easier to look at properly when nobody is standing in front of it. That is the whole reason a spare lives in the building rather than on a list of things to order.
Then write down which station it was and what you found, at the counter, on the night. Three of those and a pattern appears: the same socket, the same cover, the same roll nobody changes at the start of service. Most printers that go quiet twice go quiet for the same reason both times, and knowing which line of this list it was last time is what turns a checklist into a repair.