Layer files created by right-clicking on a network analysis sub-layer (for example stops or routes) in the table of contents and then clicking on 'Save as Layer File' are disconnected from their feature class.
Network analysis layers (for example route, closest facility, or service area layers) hold an in-memory workspace containing the feature classes that the sub-layers are referencing. If the sub-layer is saved independently to a layer file, the workspace is not saved and so the layer loses the connection to its feature class.
There are two ways to address this problem:
- Save the entire network analysis layer as a layer file instead of just saving one of the sub-layers. By saving the entire analysis layer, you are saving the workspace and feature classes that the sub-layers are referencing. Since the layer file will include all the data that the sub-layers are referencing, this layer may be large.
- Right-click on the sub-layer in the table of contents and click on 'Data > Export Data...'. This will add a new feature layer to ArcMap referencing this exported data. Save this layer to a layer file instead of the network analysis sub-layer.