If there are no Digital Signal Processors (DSPs) available on the router, then the router fails to detect the voice cards installed. You can verify this with the show diag or show version commands on the router. These commands provide information about the packet voice/data modules (PVDMs) that are installed.
PVDMs are optional components of these router platforms, with the exception of voice bundles that have one PVDM included. Cisco 3800 Series routers have four PVDM slots each. You can calculate PVDM reqiurements with the DSP Calculator tool.
The DSP Calculator tool tells you how many and what kind of PVDMs you need for your hardware and codec usage. In order to resolve the issue, install the PVDMs accordingly.