Are you on WiFi?
If yes, have is it a metered wifi (a shared 3G/4G connection), it that case the update could be blocked in order to cause cost.
You can change the wifi metered setting by going into wifi-settings for the network, looking for "network usage" (not sure what it is called in English) and change the setting from "identify automatic" to "not metered".
This will cause the update to download, but you might want to restore the setting after downloading the package.
You can also try to disable try to disable wifi and download the update over cellular data.
