An employee reports experiencing persistent neck pain and frequent headaches after starting a new job that requires long hours at a computer. They describe their workstation setup as follows: their chair is adjusted so their feet are flat on the floor with their knees at a 90-degree angle; their elbows are also at a 90-degree angle when typing; and they have to look down to see the center of their monitor. Based on this information, what is the most likely ergonomic issue causing their discomfort?