Hi,
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For your issue, error message 0x80240034 means "Update failed to download", so I would recommend to check if you have configured firewall or proxy.
How did you upgrade to Windows 10 1909? Upgrade from WSUS after approved through WSUS or through Windows Update directly which could bypass WSUS?
Does the issue occur on multiple computers or a specific computer?
Are there any error messages occur in Event Viewer\Windows logs\Application, setup, and system?
We could try general steps such as run the following command line as administrator to restart some related services.
net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver
Ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
Ren C:\Windows\System32\catroot2 Catroot2.old
net start wuauserv
net start cryptSvc
net start bits
net start msiserver
Also we could run Troubleshooter through Settings\Update&Security\Troubleshoot\Get up and running\Windows Update to check for the issue automatically.
Bests,