The Beginning Distance and/or Distance Increment are too small. Some or most of the features have no neighbors with the parameters you specified.
Use the default values by leaving the Beginning Distance and Distance Increment parameters blank. Use the measurement tool to get a feel for appropriate distances to use for the beginning and increment distances. Running the Average Nearest Neighbor or Calculate Distance Band from Neighbor Count tool can also be helpful. Remember that the distance units should match the projection and spatial reference for the Input Features you're analyzing.