When establishing the symbology of a layer in ArcGIS for Desktop 10.4, the 'Properties for All Symbols' option fails to open the Symbol Selector dialog box.
1. Click the first class in the table within the Symbology window, hold shift and click on the last class. This selects all the classes.
2. Click the header of the symbol column and select 'Properties for selected symbols'. This opens up the Symbol Selector dialog box.