Well, system update is necessary part for your device because it includes various bug fixes which make sure that your system is running normally, it also saves you from the recent threats and etc..... but one more thing your device will working fine if its not updated. But it is considered better to update the device with the latest firmware because after all its safeguarding your data. I would say try updating your device after a while it will start downloading the updates, or you could always tell me the error you are encountering while trying to update.