Hi @Stewart Pollock ,
Please use Windows PowerShell cmdlets to create and manage file download and upload transfer jobs to check if it could download successfully.
Start-BitsTransfer -Source http://officecdn.microsoft.com/pr/7ffbc6bf-bc32-4f92-8982-f9dd17fd3114/office/data/16.0.13127.21624/stream.x86.x-none.dat -Destination C:\ProgramData\Microsoft\ClickToRun\ProductReleases\2623A9B5-35EF-40AF-B907-841C96135B74\467D1B81-6125-426E-BB95-FDC7EF920714.stream.x86.x-none.1396372.dat
Here is the reference article about Managed Reference for BITS PowerShell Commands:
https://learn.microsoft.com/en-us/windows/win32/bits/bits-powershell-commands
Besides, please check if there is proxy or firewall between client and CDN.
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