The last update for v1703 was August 14, 2018—KB4343885 (OS Build 15063.1266) which you can download here from update catalog.
https://www.catalog.update.microsoft.com/Search.aspx?q=KB4343885
or you can also download the latest version here.
Windows 10 October 2020 Update
https://www.microsoft.com/en-us/software-download/windows10
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