Hi Kirstin,
I am too facing the same problem. Did you find a solution to this problem?
Most symbol types can be used with a feature service; however, in some cases, the symbols may be downgraded.
For line layers, simple line symbols are supported. If other symbols are used, the feature service converts them to a simple line symbol that best represents the original symbol. For example, a cartographic line symbol in the map document may be drawn as a simple solid line in a feature service client. If a line symbol is complex or has multiple layers, the feature service downgrades the line to best represent the original line symbol.
For polygon layers, simple fill and picture fill symbols are supported. If other symbols are used, the feature service downgrades them to simple fill symbols. For multilayer fill symbols, the feature service only considers the top layer. Also, a fill symbol's outline symbol has the same level of support as described for line layers above.
For point layers, simple marker and picture marker symbols are supported. If other symbols are used, the feature service downgrades them to picture marker symbols. Multilayer marker symbols are also downgraded to picture marker symbols where the layers are merged into a single layer. Mask properties, where a halo can be set for a marker symbol, are not supported.