The errors are quite hard to track. There is not a single list. So, here, for your convenience:
#define NRF_ERROR_BASE_NUM (0x0) ///< Global error base
#define NRF_ERROR_SDM_BASE_NUM (0x1000) ///< SDM error base
#define NRF_ERROR_SOC_BASE_NUM (0x2000) ///< SoC error base
#define NRF_ERROR_STK_BASE_NUM (0x3000) ///< STK error base
Global errors:
#define NRF_SUCCESS (NRF_ERROR_BASE_NUM + 0) ///< Successful command
#define NRF_ERROR_SVC_HANDLER_MISSING (NRF_ERROR_BASE_NUM + 1) ///< SVC handler is missing
#define NRF_ERROR_SOFTDEVICE_NOT_ENABLED (NRF_ERROR_BASE_NUM + 2) ///< SoftDevice has not been enabled
#define NRF_ERROR_INTERNAL (NRF_ERROR_BASE_NUM + 3) ///< Internal Error
#define NRF_ERROR_NO_MEM (NRF_ERROR_BASE_NUM + 4) ///< No Memory for operation
#define NRF_ERROR_NOT_FOUND (NRF_ERROR_BASE_NUM + 5) ///< Not found
#define NRF_ERROR_NOT_SUPPORTED (NRF_ERROR_BASE_NUM + 6) ///< Not supported
#define NRF_ERROR_INVALID_PARAM (NRF_ERROR_BASE_NUM + 7) ///< Invalid Parameter
#define NRF_ERROR_INVALID_STATE (NRF_ERROR_BASE_NUM + 8) ///< Invalid state, operation disallowed in this state
#define NRF_ERROR_INVALID_LENGTH (NRF_ERROR_BASE_NUM + 9) ///< Invalid Length
#define NRF_ERROR_INVALID_FLAGS (NRF_ERROR_BASE_NUM + 10) ///< Invalid Flags
#define NRF_ERROR_INVALID_DATA (NRF_ERROR_BASE_NUM + 11) ///< Invalid Data
#define NRF_ERROR_DATA_SIZE (NRF_ERROR_BASE_NUM + 12) ///< Data size exceeds limit
#define NRF_ERROR_TIMEOUT (NRF_ERROR_BASE_NUM + 13) ///< Operation timed out
#define NRF_ERROR_NULL (NRF_ERROR_BASE_NUM + 14) ///< Null Pointer
#define NRF_ERROR_FORBIDDEN (NRF_ERROR_BASE_NUM + 15) ///< Forbidden Operation
#define NRF_ERROR_INVALID_ADDR (NRF_ERROR_BASE_NUM + 16) ///< Bad Memory Address
#define NRF_ERROR_BUSY (NRF_ERROR_BASE_NUM + 17) ///< Busy
STK errors are of the form 0x3...
:
#define NRF_L2CAP_ERR_BASE (NRF_ERROR_STK_BASE_NUM+0x100) /**< L2CAP specific errors. */
#define NRF_GAP_ERR_BASE (NRF_ERROR_STK_BASE_NUM+0x200) /**< GAP specific errors. */
#define NRF_GATTC_ERR_BASE (NRF_ERROR_STK_BASE_NUM+0x300) /**< GATT client specific errors. */
#define NRF_GATTS_ERR_BASE (NRF_ERROR_STK_BASE_NUM+0x400) /**< GATT server specific errors. */