Hallo,
solved, our Firewall was the problem.
So I solved the Error: ng build --prod does not copy any web.config file. So I copy it additionally !
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<system.webServer>
<staticContent>
<remove fileExtension=".json" />
<mimeMap fileExtension=".json" mimeType="application/json" />
<mimeMap fileExtension="woff" mimeType="application/font-woff" />
<mimeMap fileExtension="woff2" mimeType="application/font-woff" />
</staticContent>
<!-- IIS URL Rewrite for Angular routes -->
<rewrite>
<rules>
<rule name="Angular Routes" stopProcessing="true">
<match url=".*" />
<conditions logicalGrouping="MatchAll">
<add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" />
<add input="{REQUEST_URI}" pattern="^/(api)" negate="true" />
</conditions>
<action type="Rewrite" url="/" />
</rule>
</rules>
</rewrite>
</system.webServer>
</configuration>
Yes, it looks similar.
Product is Angular and the framwork is .net core