X-carve z axis rod not moving

hello! my x-carve z axis is moving up and down. the stepper motor and the gears are spinning but the rod is not rotating and therefore not moving the z axis. Any idea how to trouble shoot? this happened after a power shutdown in the middle of a carve.

Thanks so much!

check if the little set screws on your z-axis pullies are loose or missing. tighten them with blue loctite