Hi,
As per the OS support matrix, DL20 Gen9 does not support Windows 2019 : http://h17007.www1.hpe.com/us/en/enterprise/servers/supportmatrix/windows.aspx#.XHdsXYhLiUk
1. What is the controller being used?
2. Could you try installing Windows 2016 instead?
3. How are you trying to install the OS? Through IP or is it a manual installation?
Regards,
Shruthi (HPE Employee)
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