DIAGNOSIS The warming plate is a separate, lower-wattage heating element. The connection to it has likely corroded or the element itself has failed.
FIX Unplug the machine. Remove the bottom plate. Locate the two spade terminals connected to the warming plate element at the base of the unit. Check for corrosion or loose connections. Clean terminals with electrical contact cleaner. Ensure they are snug.
IF THAT DIDN'T WORK The warming plate element is likely burned out. Test it for continuity with a multimeter. If it's open (no continuity), you must replace the entire warming plate assembly. It's not a user-serviceable part.
HEADS UP The stainless steel carafe is not insulated. It relies entirely on the warming plate. A failing plate is a common failure point on these models. Do not attempt to bypass or modify the element wiring.