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Fix ASP.NET and IIS errors on Windows hosting

Find the cause of ASP.NET errors on Windows hosting: read the 500.xx sub-code, turn on the ASP.NET Core stdout log, fix web.config and SQL Server errors.

  • Intermediate
  • 20 min read
  • Updated
On this page
  1. Step 1: Note the exact code
  2. 500.19: configuration data is invalid
  3. 500.30, 500.31 and 502.5: the app does not start (ASP.NET Core)
  4. 403.14 Forbidden: the directory listing is denied
  5. SQL Server: "The certificate chain was issued by an authority that is not trusted"
  6. Next steps

On Windows hosting your site runs on IIS. When a request fails, IIS shows an HTTP status with a sub-code after the dot, such as 500.19 or 500.30. That sub-code tells you where to look. This guide covers the codes you meet most often and how to read the details.

Step 1: Note the exact code

Open the failing page and note the full code and any HRESULT value (for example 0x8007000d). Then make the details visible:

ASP.NET Core

  1. In httpdocs, create a folder named logs.
  2. In web.config, set stdoutLogEnabled="true" and stdoutLogFile=".\logs\stdout" on the aspNetCore element:
XML
<aspNetCore processPath="dotnet"
      arguments=".\MyApp.dll"
      stdoutLogEnabled="true"
      stdoutLogFile=".\logs\stdout" />
  1. Reload the page and open the newest stdout_….log file in logs.
  2. Set stdoutLogEnabled="false" again when you are done.

ASP.NET (.NET Framework)

Turn custom errors off for a moment so that ASP.NET shows the full exception. In Plesk, use the domain's ASP.NET Settings, or set this in web.config:

XML
<system.web>
  <customErrors mode="Off" />
</system.web>

Set it back to RemoteOnly or On as soon as you have the message: the details are visible to everyone.

500.19: configuration data is invalid

IIS cannot read web.config. The HRESULT names the reason:

HRESULTCauseFix
0x8007000dMalformed XML, or a section for a module the server does not have (for ASP.NET Core: the hosting bundle for your version)Check the line named in the error; remove sections you do not need; ask us about the .NET version
0x80070021The section is locked at server level and cannot be set in your web.configRemove that section from web.config, or ask us whether the setting can be changed for you
0x800700b7A duplicate entry for a setting that is already defined higher upRemove the duplicate entry from your web.config
0x80070003IIS cannot read the configuration file at the site's pathMake sure web.config is in httpdocs

500.30, 500.31 and 502.5: the app does not start (ASP.NET Core)

  • 500.31 Failed to Find Native Dependencies: the .NET runtime your app targets is not installed on the server. Target a version the server has, or publish self-contained. Ask us which versions are available.
  • 500.30 In-Process Startup Failure: the app fails while starting. The stdout log shows the exception, often a missing setting or a failed database connection at start-up.
  • 502.5 Process Failure: the app's process does not start, often for the same reason as 500.31.
  • 500.32 Failed to Load dll: the app was published for a different processor architecture (for example 32-bit against 64-bit). Republish framework-dependent, without a runtime identifier.

403.14 Forbidden: the directory listing is denied

IIS found no application and no default page. Usually the deployment is incomplete: the files are in the wrong folder, some were not copied, or web.config is missing. Upload the complete publish output into httpdocs.

SQL Server: "The certificate chain was issued by an authority that is not trusted"

Since Microsoft.Data.SqlClient 4.0, connections are encrypted by default and the driver checks the server's certificate. If your app cannot verify it, the connection fails with this message.

  • Ask us in a ticket for the recommended connection settings for your server.
  • To connect with encryption but without checking the certificate, add TrustServerCertificate=True to the connection string. Microsoft notes that this leaves the connection open to interception, so treat it as a temporary step.

Login failed for user. The user name or password in the connection string does not match the database user in Plesk, or the user is not assigned to that database. Set a new password for the user in Plesk and update the connection string.

Next steps

Frequently asked questions

Why do I only see a generic error page?

IIS and ASP.NET hide error details from visitors on purpose. Use the stdout log (ASP.NET Core) or turn custom errors off for a moment (ASP.NET) to see the real message.

The app works on my computer but not on the hosting. Why?

Most often the .NET version on the server differs from the one you target, a setting such as the connection string still points to your computer, or a file is missing from the upload.

Can I see the Windows event log or IIS Manager?

Not on shared Windows hosting; we manage the server. Plesk shows your site's web server logs under Logs. For more, send us the time and address of the failing request in a ticket.

Can I leave the stdout log on?

No. Microsoft warns that it has no size limit and can fill the disk. Turn it on to find a problem, then off again.

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