Hi,
It seems you have a proxy server and AAD Connect is trying to connect to Azure but fails, you will have to open up machine.config to make the changes.
If you're using an outbound proxy for connecting to the internet, the following setting in the C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config file must be added for the installation wizard and Azure AD Connect sync to be able to connect to the internet and Azure AD.
<system.net>
<defaultProxy>
<proxy
usesystemdefault="true"
proxyaddress="http://<PROXYADDRESS>:<PROXYPORT>"
bypassonlocal="true"
/>
</defaultProxy>
</system.net>
Also check PowerShell and .Net version, the Azure AD Connect depends on Microsoft PowerShell 5.0 and .NET Framework 4.5.1. You need this version or a later version installed on your server.
Hope this helps.
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