It could look like the stack is generating a BLE_GATTS_EVT_SYS_ATTR_MISSING event when you read the handle which contains the CCCD. The state of this value is unknown until the handle is either written to or sd_ble_gatts_sys_attr_set() is called with NULL or the saved parameters from an earlier connection through sd_ble_gatts_sys_attr_get(). If the application does not reply to this event, the ATT transaction will time out after 30 seconds and subsequent ATT traffic will be disallowed per the spec.
It could look like the stack is generating a BLE_GATTS_EVT_SYS_ATTR_MISSING event when you read the handle which contains the CCCD. The state of this value is unknown until the handle is either written to or sd_ble_gatts_sys_attr_set() is called with NULL or the saved parameters from an earlier connection through sd_ble_gatts_sys_attr_get(). If the application does not reply to this event, the ATT transaction will time out after 30 seconds and subsequent ATT traffic will be disallowed per the spec.
