Yes, you guessed correctly. It turns out that the two sub-layers that were not available for me to use in the attribute table were symbolized by a combination of two fields in my MXD. The Attribute Table widget requires that the Feature Access capability be enabled in the map service that contains the sub-layers you want to see in the attribute table. But the Feature Access capability is not available for features that have been symbolized using multiple fields.
So, if I want to use the Attribute Table widget, the only thing I can do is reorganize how I publish my layers and how those layers are symbolized. The end result is that I'll have to go from one map service with three sublayers, to three services and nine sublayers. All because the multiple-field renderer is not supported by the Feature Access capability. That's too bad.
So, if I want to use the Attribute Table widget, the only thing I can do is reorganize how I publish my layers and how those layers are symbolized. The end result is that I'll have to go from one map service with three sublayers, to three services and nine sublayers. All because the multiple-field renderer is not supported by the Feature Access capability. That's too bad.