After upgrading from 9.x requests to /api throw "404 - not found"

If after upgrading your self-hosted helpdesk from "9.x" to "10.x" or "11.x" on a Windows Server all API calls start returning "404 - File or Directory not found" try this:

Open the file located at

C:\Windows\System32\inetsrv\Config\applicationHost.config

and check if there's a section that configures access to "/api" location. Something like:

<location path="Default Web Site/helpdesk/api">
    <system.webServer>
        <security>
            <authentication>
                <anonymousAuthentication enabled="true" />
            </authentication>
        </security>
    </system.webServer> 
</location>

Simply remove that section and it should work. It was required for older versions, but not the one based on ".NET Core" (aka NET 6,7,8 and later)