ASP.NET Core 8.0 Web API on IIS 10 - Intermittent 404 Not Found

Question

I recently published a .NET 8 Web API to IIS Windows server. At first I was getting errors showing

Failed to Load ASP.NET runtime

which I resolved by installing ASP.NET Core Runtime 8.0.5 Windows Hosting Bundle. Then the API seemed to be working fine.

The next day calling the API in Postman I got

404 Not Found

I've done the following:

• project is working fine in debug on my dev pc.
• checked my domain is pointing to the correct IP address
• app pool does NOT show in Worker Processes
• re-started the Website/App pool in IIS
• re-started IIS
• checked Windows events - can't see anything related.
• checked IIS log file - seems to be mostly empty.

Has anyone experienced this or know how to troubleshoot it?

Web.config

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <location path="." inheritInChildApplications="false">
    <system.webServer>
      <handlers>
        <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModuleV2" resourceType="Unspecified" />
      </handlers>
      <aspNetCore processPath="dotnet" arguments=".\SamadhiAPI.dll" stdoutLogEnabled="true" stdoutLogFile=".\logs\stdout" hostingModel="inprocess" />
    </system.webServer>
  </location>
</configuration>
<!--ProjectGuid: b7f93657-cfc6-4b8d-91d7-33f7e9e4960b-->

Answer 1

Troubleshooting errors can be frustrating as often the error message is not in fact the cause of the problem. In my case, the intermittent behavior of the web service was caused by a conflicting subdomain DNS entry.