Almost every counter that goes quiet has lost one of three things. Each one looks the same from the front, and each one has a different fix.
A counter that has gone quiet looks identical from the front whichever way it broke. The people standing in front of it see nothing coming out, the staff behind it see no new tickets, and each end assumes the fault belongs to the other. Whoever is responsible for the site gets told the same sentence every time — that counter has stopped — and that sentence on its own is not something anybody can act on.
Almost every version of it comes down to the paper, the power or the signal. They are worth learning in that order, because that is roughly the order of how often they happen and how quickly they can be put right. Paper is a minute's work by whoever is already standing there. Power is usually a lead. Signal is the one that needs somebody who knows the building. Asking the three in order turns a vague report into a fix.
Paper is the only one of the three that fails on a schedule you can predict. A roll holds a known number of tickets and a busy counter works steadily through it, so the counter that has been printing all evening is the one most likely to run dry next. It is also the most misleading failure of the three: the order arrived, the printer took it, and nothing came out, so the staff conclude that something has been dropped when the machine is simply empty.
Power problems are rarely the building. They are a lead pulled out by a chair, a printer switched off at its own switch during a clean-down, a device flat because it was never plugged back in after the briefing, or a shared socket somebody borrowed for a kettle. All of them present as a dead counter, and all of them are found by looking at the back of the equipment rather than at the software.
Signal is the one nobody can see, and the only one of the three worth testing before doors. Coverage inside a venue is never uniform: a bar built under a stand, a kitchen behind a block wall, or a counter in the far corner of a field can sit in a dead spot the rest of the site has no trouble with. It also changes once the place fills up, so a check made on an empty floor is not the same check. Test from the counter itself, standing where the staff will stand, with the equipment where it will actually live.
The reason to name the three is that it makes a quiet counter answerable. Somebody walks to it, looks at the paper, looks at the leads, prints a test ticket, and comes back able to say which of the three it was. That takes one person and no argument, and it means the fix happens at the counter instead of being discussed elsewhere while orders keep arriving.