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Try turning the register key (or, manager key) to
Z, X, P, or SM modes. If CLOSED still shows up in those modes, something is wrong with the register and it would need servicing (or replacing.)
If CLOSED only shows in REG and in VOID modes only, then that's normal enough... you need to press
(Or try pressing the 1 key then the CLERK key. Or pressing 2 key then CLERK key.)