If the battery failed, your machine is "forgetting" who it is.
The message on a Sinumerik 810D typically indicates a communication failure between the operator interface (HMI/PCU) and the Numerical Control Kernel (NCK) . This often occurs when the NCK fails to boot correctly or has lost its internal memory due to hardware or power issues. Common Causes
controller on the vertical machining centre stared back with a cold, persistent message scrolling across the screen: "Waiting for NCK connection."