Doesn't go on. Check: Has fuse on house circuit blown? If basement is flooded and fuse box is down there, don't go near it until you shut off the house current at the meter. Is there trouble in the motor? See
motor, electric. Did float fail to rise with the water level in the sump? Clean the rod on which it is mounted with steel wool and coat lightly with grease. If this doesn't correct the problem, float may have a hole in it and be waterlogged. Remove, empty, and solder hole, or cover with plastic steel; or buy a new float.
Motor working but pump not pumping. Check whether sump is filled with muck and pump intake is clogged. If these are okay, call a serviceman.
Note. Don't fool around in a sump without first turning off the electricity to the motor.