Your layer is for one geometry type, but the data source is another type. For example, the layer symbolizes points, but the underlying data source is polygon.
- Remove the layer from your document.
- Alternatively, repair the layer by referencing the proper feature type for your data source.
Referencing the wrong data source could occur if your layer was broken at some point and you used the Repair Data Source command to fix the layer but picked the incorrect feature class with another geometry type.