Issue with Symbology: Not all features appearing in Legend

[SophiaMisiakiewicz]

When is use the "Apply Symbology from Layer" geoprocessing tool the Symbology Classes does not appear correctly. It will only display features present in map and not all features that should be in the Legend. For example, if I don't have a Weir on my map the  symbology for a Weir will not appear in the Symbology Classes but I want it to without having to input it in manually every time. 

[ToddW_stl]

Is there a Weir in your source data with the desired symbol applied?  Are the data values for Weir the same in the source and target data (i.e. "Weir" or "weir" or "WEIR")?

[Laura]

The expected outcome always works for me when I use 'Import Symbology' from right within the symbology pane.