Remove the peristaltic pump assembly from the motor (this can be done by turning the clear plastic housing counterclockwise a partial turn and popping it out). Inspect the tubing and rollers for any obstructions (cured TSL/ISO). Ensure the motor rotor can spin by manually running the ISO lube pump (this can be done by pressing the override button on the Diagnostics screen).
NOTE: motor rotor can be difficult to spin with fingers. This alone does not indicate the motor is bad.
Check wiring for touching wires.