Hi @adil
Here is an official article helps fix Microsoft .NET Framework 3.5 installation errors:
https://learn.microsoft.com/en-us/troubleshoot/windows-client/application-management/dotnet-framework-35-installation-error#error-code-0x800f081f
You may receive the following errors when you install the .NET Framework 3.5 in Windows Server:
Error code 0x800F0906
Error code 0x800F081F
Error code 0x800F0907
You could check the error code in error message and find it in the article.
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