DIAGNOSIS That's almost always a dead bake element. It's the big metal coil at the bottom of the oven cavity, and it's the most common heating element to fail. The broil element might still work, but you'll get no heat from the bake setting.
FIX Unplug the range. Pull the oven rack out. You'll see the bake element held in by two screws at the front. Unscrew them, then gently pull the element forward just enough to access the back connections. There are two wires, usually held by spade connectors. Pull them straight off. Take the old element to an appliance parts store to match it (or use model number JB645RKSS). Plug the new wires on, screw the element back in, plug the range in, and test.
IF THAT DIDN'T WORK If the new bake element still doesn't glow, the issue could be the oven control board not sending power. You'd need a multimeter to test for 240V at the element terminals when the oven is set to bake. If there's no power, the board is likely the culprit.
HEADS UP Don't just assume it's the broil element because you see it glowing when you use the broil function. They're independent. The bake one is the one on the very bottom.