No ice, hollow cubes, or a bin that has fused into one solid block. The ice maker is the part of a refrigerator most likely to fail first and most likely to be misdiagnosed.
Work backwards along the water path. The supply valve behind the refrigerator, the fill tube, the inlet valve, then the module itself. A frozen fill tube is extremely common and looks exactly like a dead ice maker, and it points at a different underlying fault, usually a fill valve that leaks slightly or a freezer running too cold.
On built-in and column units, dedicated ice makers have their own drain and their own condenser, and both need attention on a schedule that almost nobody keeps.
Low water pressure or a partially blocked inlet valve, most of the time. If the household has a reverse osmosis system feeding the fridge, the pressure is often too low for the ice maker specifically, and that is a plumbing conversation rather than an appliance one.
Cubes that fuse together mean they are melting slightly and refreezing. Either the freezer is cycling warm, the door is not sealing, or the ice is simply sitting there for months. If you use ice rarely, that last one is normal and not a fault.
Air in the line, usually. Run several litres through the dispenser and give it 24 hours before assuming anything failed.
Usually yes. It is a self-contained assembly, and replacing the whole refrigerator over an ice maker rarely makes sense.