DIAGNOSIS The top spray arm isn't getting enough water pressure or is obstructed. This is a common complaint with this model's tall tub design.
FIX Remove the top rack. Manually spin the upper spray arm. It should move freely. Check each nozzle for clogs. Use a toothpick to clear any debris. Ensure nothing tall on the bottom rack is blocking the arm's rotation.
IF THAT DIDN'T WORK You may be overloading the lower racks. This blocks water from reaching the top arm. Leave more space between items on the bottom. Use the 'Top Rack Only' cycle for just glasses.
HEADS UP Avoid placing large bowls or pans on the left side of the bottom rack. They can directly block the water jet that feeds the upper spray arm.