A layer in your map is rendered using an unsupported dot density option.
- Specify fixed placement for dots. Click the Properties button on the Symbology tab and click Fixed Placement.
- Alternatively, remove the map layer that uses the Non-fixed Placement option.
When using the dot density renderer to symbolize a layer in a basemap layer, you must use the Fixed Placement option for dot placement. Fixed Placement freezes the placement of dots as the map is refreshed.
See Using dot density layers for more information.