CYBLE_ERROR_INVALID_OPERATION with CyBle_GattcDiscoverAllCharacteristics

I'm making a project similar to the BLE_UART project from cypress using the CY8CKIT-042-BLE Pioneer Kit with a CYBLE-EVAL-014008 module and the provided dongle. During the initial connection, I'm getting the error CYBLE_ERROR_INVALID_OPERATION whenever I call the function CyBle_GattcDiscoverAllCharacteristics(cyBle_connHandle, attrHandleRange);

Why would that function throw that error? My attrHandleRange object uses the same BLE UART Service Handle start and end as the BLE_UART project on the central side, so I imagine this is an issue in the peripheral code.

Thanks for any help.