Common Incapsula Errors and Their Solutions

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When the Incapsula platform encounters an issue, it sends the appropriate teams an error page with a specific error. There are various reasons for an error message, and we troubleshoot each situation differently. For your convenience we gathered a list of common errors, explain what they mean, and suggest how to troubleshoot them.

Connectivity errors: 

Error code 20

Error code 8

Security errors: 

Error codes 14-17

SSL errors:

Error codes 29

Error code 26

Resolving error:

Error codes 22

Error code 39

Violation of terms:

Error codes 18


Error code 20

General description : Request was not completed due to a failure to connect to the server - TCP Timeout


The Error code 20 is a timeout connection error, which indicates that Incapsula was not able to connect to the origin server. As a result the user will see an Error code 20.

This problem may happen due to these reasons:

  • The Incapsula IPs are not whitelisted on the origin server or firewall, as a result that a server or firewall may block or perform a rate limiting on the Incapsula IPs. Please read this article for more information.

  • The server is malfunctioning and dropping requests.

  • The origin server is taking too long to respond to the request.

  • There’s a local issue with an upstream provider.

  • There are network issues between Incapsula and the origin server. You may monitor the Incapsula network here.


Making sure that Incapsula IPs are whitelisted and the origin server is restricted to direct access in most cases will resolve the issue. You may find the list of Incapsula IPs here.

Please also make sure that the origin server is up and running with no faults.

Check with your hosting provider to assist you with applying the required restrictions and whitelists.

We’ve listed the reasons that are the most common causes for triggering an Error code 20, but they are not the only reasons. If you require any assistance, please contact Incapsula support for further investigation.


Error code 8

General description : Request was not responded due to a failure to connect to server - TCP RST


This code indicates that the origin server rejected Incapsula proxies when it tried to establish a TCP connection. The difference between error 8 and error 20 is that in this particular case Incapsula was actively rejected by the origin server. The troubleshooting steps for this error is the same as Error code 20 listed above.


Error codes 14-17

General description : Request was blocked due to your site's security rules.




In order to determine the exact reason why the user was blocked, we will assign you an Incapsula incident ID, which you can see in My Console.

Check the Events Tab in your Incapsula console. You can filter the incident ID and find the security event. If you see that the user is legit (false positive), please contact Incapsula support.


Error code 29

General description : SSL is not supported


This error states that a user was trying to establish SSL connection to the site, While the web server doesn't support this kind of connection.

This problem may happen due to these reasons:

  • SSL is not enabled on Incapsula while the site's web server has an installed certificate.

  • The web server does not have a certificate installed on it.

  • Port 443 is not open on the web server side.


Please verify that port 443 is indeed open on the server side. Make sure that you have generated an Incapsula certificate (paid plans only) or uploaded your own custom one (Business and Enterprise plans only). Please contact support if your site does support SSL, and the Incapsula server hasn't detected it as one.


 Error Code 26

General description : Request was not completed due to a failed SSL connection to web server.

This error is triggered when the Incapsula proxy is not able to complete the SSL handshake with the origin server.

This problem may happen due to these reasons:

  • Your custom certificate was uploaded incorrectly to Incapsula proxies.

  • No certificate is installed on the web server. Port 443 is closed on the server side.

  • The web server may not support the specific SSL protocol that Incapsula tried to connect with.

The troubleshooting will be the same as Error code 29.

If you still see the error after troubleshooting, please contact support to verify that Incapsula used a supported web server's SSL protocol.


Error code 22 

 General description : Incapsula cannot resolve the site from its host name.


This problem may happen due to these reasons:

  • The site's DNS records were not input correctly.

  • A site was removed from Incapsula however it is still pointing to our records/IPs.

  • The site was recently added to the service and the DNS changes have not yet propagated.

  • Performing A record re-use without CNAME re-use is in place to a site that is not protected by the Incapsula service.


Make sure the DNS records are accurate.

Note: A record re-use is not a supported feature without CNAME re-using in place and will result with the error, however CNAME re-use by itself is supported (only for Enterprise clients).


Error code 18   

 General description : Site is no longer under service due to violation of terms of use.


A site may be null routed due to the following:

  • A site without proper DDoS mitigation coverage is under DDoS attack.

  • Charge failure.

  • Violation of Incapsula terms of use.

If these solutions work for you, please let us know. We’d love to hear what worked. If you still need help resolving an error, please contact the support team with the specifics of your case.


Error code 39

General description: The site is pointing to the wrong IP / A record.

Since our new network provides a network slice for each customer, and an IP per account, all sites must point to the proper IP.


Make sure that your site is pointing to the proper A record. 

Click the "Status" icon on your Websites page to view the correct site configuration. 


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