DNN error site unavailable – Why does it happen?

why does dns error happens

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DotNetNuke aka DNN is one of the great choices for setting up a website portal. It is known for its speed and offers thorough security.

It works based on the underlying database. Therefore, any problem with database server connection can result in DNN error site unavailable.

At 1 ONLYHOST, we often come across these tricky DNN errors as part of our Server Management Services.

Today, we’ll see top reasons for the error and how our DNN experts fix DNN error site unavailable.


How does DNN Site Unavailable error look like?

Often, when you access DNN websites, it may show up the typical site unavailable error as:

DotNetNuke uses a MSSQL database to store all the details related to the website. It provides a flexible way to control access to various pages and content on the website.

In general, DNN shows the Under Construction page when it is unable to connect to the SQL database.


DNN error site unavailable – Causes and Fixes

We just saw how the site unavailable error looks like. It’s time now to see the typical reasons that would cause this error. And, how our Dedicated Engineers fix site unavailable error with our expertise in managing DNN websites.


1. MSSQL server down

One of the obvious reasons for MSSQL would be MSSQL server being down on the server. When SQL server stop serving databases, the website would show up the site unavailable error. The SQL server can go offline due to reasons including hardware failure, resource crunch on the server, etc.


How we fix

To make, the website up and running, we need to make MSSQL server running.  Therefore, our Windows Engineers restart MSSQL server on the server from:

All programs → Microsoft SQL Server → SQL Server Configuration Manager → SQL Server Services → Right Click service and select restart.

Or from the command-line

C:\>net start MSSQLSERVER 

This will start SQL Server Service on server. Additionally, if the server has some control panels like Plesk, service can be restarted from the panel too. However, in all cases, it’s worth to check on the reason for MSSQL failure to avoid repeated problems.


2. Incorrect database connection string

Again, one of the major reasons for DNN site unavailable error would be wrong SiteSqlServer connection string value in web.config file. This causes the issue with connection to the domain database.

Usually, this occurs during DNN website migration to a different server.

When website uses sql server sql authentication, the connection string would appear as:

<add name="SiteSqlServer" connectionString="Server=(local);Database=DotNetNuke;uid=;pwd=;" providerName="System.Data.SqlClient" />

The connection information of any website can be retrieved from Plesk control panel.

In cases of restoring an SQL database to a new server, the DNN user also will be copied. However, the DNN user will not be present on the new server. This causes website database connection to fail.


How we fix DNN connection string?

We check the SiteSqlServer connection string value in web.config file. Then try to connect the db server using same credentials from command line. We verify the SQL host server details and correct typos if any.

When restoring the SQL to another server, we re-create the database user ID and password first. Then, our Dedicated Engineers look at the Database roles and change all the ASPnet related roles to the new user. Also, this involves deletion of the invalid database user from the old server too.


3. Application pool crash

In Windows web servers, each website has it’s own unique application pool or worker process. It is this process that serves the website in the browser.

When the website code has a flaw or consumes too much memory resources, it can cause an application pool crash.  Even, the addition of a new module can affect the memory usage of the website. And, when the worker process crashes multiple times, the application pool will not launch any more worker processes. As a result, DotNetNuke website show the error.

Similarly, application pool can crash when the server restarts the SQL service. Restarting the SQL service while the site is active will break the connection to the database and show up the under construction page.


How we fix Application pool?

The solution for this problem is restarting the Application Pool of the DNN website.

For example in servers with Plesk control panel, we restart application pool of the domain from Websites & Domains >> Domain >> Recycle option

And, in servers with out control panel, our Dedicated Engineers follow these steps to recycle application pool.

  • Connect to the server via rdesktop.
  • Start -> Administrative Tools -> Internet Information Services (IIS) Manager.
  • Expand the server and click on “Application Pools”.
  • In the center window, right-click the Application Pool for the website and select “Recycling...”

That fixes the website error and DNN starts loading again.

[Is your DNN website showing Site Unavailable error? Our Experts can fix it right away.]



To be precise, DNN error site unavailable happens mainly due to wrong database connection string, MSSQL server unavailability and many more. Today, we saw how our Dedicated Engineers fix it by correcting database details, restarting application pool, etc.

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