Users might experience problems while visiting their DNN site such as having pages return 404 errors, redirection loops, or the entire site responding with a 502/503 HTTP error. This article explains how to correctly troubleshoot those issues.
Review the application logs
Similar to other issues with DNN, it is always important to check the Application Log files as well as the Admin Logs whenever one experiences a problem loading the page as it is likely there would be a matching error detailing the problem which would help with the troubleshooting process, and might even be already documented in the knowledgebase (e.g. The length of the URL for this request exceeds the configured maxUrlLength value)
Review requested page
A 404 error suggests the page cannot be found. Thus, one of the first things to do is ensure the used URL is valid and we are requesting a page or path that exists in the DNN instance.
Check the content item slug
As mentioned in Accessing visualizer slug returns a 404 error, using an incorrect slug might lead to a 404 response when requesting the content item.
Review the settings and add query string
In some instances, DNN will try to rewrite the requested URL into a friendly one turning a query string into a path. Thus, one can check the existing settings for this area, and exclude the query string from being rewritten by following the Custom Querystrings Are Being Rewritten article.
Review Friendly URL and AUM settings
If unwanted redirections are leading to a 404, it is recommended to ensure one is using the advanced friendly URL format as mentioned in Enabling Friendly URL Rewriting and also review some other factors that might lead to redirections as stated in Managing redirects and Advanced URL Management in DNN.
Test URL rewrite
DNN comes with a Test URL function that is very useful in explaining how a URL is being managed and the reason for the rewrite/redirection. For further information, check Test URL Generation.
Review the page details
This is a broad area, but one would need to check the specific area returning a 404 and then reference the relevant resources for that area. For instance, if one is finding this error in Profile pages, one can follow View Profile displays 404 error. Similarly, if the problem is with pages having an outdated URL with .aspx at the end, one can check Certain pages in portal leads to a 404 error.
Review possible reasons
A 502/503 would indicate the server is not responding as expected which might be due to planned maintenance or an emergency change as mentioned in Production Environments Down with 502 Bad Gateway Response Error. If the issue persists, one needs to contact support.
Report OnDemand Issue
If the problem persists and your site (Production or Sandbox environment) continues to return a 502 or 503, you can contact support following the instructions in the Reporting a Site Outage as an OnDemand customer article.
Check proxy and webserver
Users managing their own infrastructure would need to review their proxy/gateway and webserver to ensure they are responding and have the correct settings. A 502 would generally suggest the webserver is not sending a valid response so one would need to make sure it is running and search for any errors or configuration issues.
Update module or contact vendor
If the page is affected by a third-party module it is always recommended to ensure the version of the module being used is compatible with your DNN version and to update it if this is not the case. If the problem persists, the next recommended step would be to contact the vendor/developer as they would be familiar with the component.
Generally, the error message on the page would contain some details as per the affected module and the reason behind it. Thus, one is encouraged to search for that specific error on our knowledge base as it is likely the problem and solution are already documented.
Receiving the ERR_TOO_MANY_REDIRECTS message while visiting the page might have different causes as mentioned in the article Redirection error redirected you too many times, and one can follow the guidance there to review some common areas.
If one is running a version older than 9.2 and is experiencing a redirection loop on their site along with server errors, it is likely they are affected by a known defect as described in DNN Evoq 9.1.1 Error: A critical error has occurred, and upgrading their DNN installation would be the permanent solution.
If the problem persists after following the guidelines above, one can Contact Support with the information below to further troubleshoot the issue.
- Details of the issue experienced such as reproduction steps and expected behavior.
- Log files and screenshots of the problem.
- (If applicable) Any other details such as the results of running the Test URL function.
- A HAR file generated while reproducing the problem.
- (If applicable) The IIS logs.
<supportagent>Note that one can visit the page in a specific IIS log entry by using the path and query string (e.g mysite.com/Default.aspx?tabid=123&...). Alternatively, with access to the instance, one can query the database to find the page using the tabid (SELECT * FROM Tabs WHERE TabID = 123)</supportagent>