Description
This error is triggered when (1) the unique ID field specified is not of type integer (short or long) or (2) the values in the specified unique ID field are not unique. This tool requires a unique ID field to match results to corresponding input features.
Solution
If your dataset doesn't have a unique ID field, you can create one. First, add a new field to your input dataset that is of type LONG or SHORT. Then, use the Calculate Field tool to set the new field values to the FID or ObjectID field values.