License Troubleshooting

From WHMCS Documentation

If you are encountering a licensing error when accessing your WHMCS installation's administration area, this could indicate that your server is unable to communicate with our license server. This page details the most common errors and provides some suggested resolutions.

License Invalid

A Licence Invalid error on the admin login page can be caused by one of the following changes:

  • The license key has been entered incorrectly

Please ensure the full key is entered, this includes the prefix eg. "Leased-", "Owned-", "WebHost-", "WHMCS-" and "Dev-".

  • The domain being used to access your install has changed
  • The IP address your install is located on has changed
  • The directory you are using has changed

Following any changes to the location of your WHMCS installation, the license must be updated accordingly. Please refer to Moving WHMCS for instructions on doing so.

Specific Errors

Required function base64_decode is not available

This error indicates that your server has the required base64_decode function disabled in your PHP configuration. Please adjust your website's PHP configuration so as to enable the base64_decode function.

It may be necessary for the function to be added at the server level. The following links might be helpful in accomplishing this on your server:

If you need further assistance, you may need to reach out to your web host or systems administrator to resolve this.

Required function is not available

This error will appear when a necessary CURL function has not been installed on your server or is disabled in the configuration. The error message will specify the required function which has been disabled, eg:

  • curl_init
  • curl_setopt
  • curl_exec
  • curl_getinfo
  • curl_error
  • curl_close

All of these functions must be installed and enabled on your server in order to properly validate your license. You can check to see if these functions are available on your server by:

  1. Creating a PHP Info page, as described in the PHP Documentation
  2. Visiting the PHPInfo page in your browser
  3. Referring to the "disable_functions" section
  4. If the functions in the above listed are present under disable_functions, the functions are disabled on your server. It will be necessary to enable them to resolve the licence error.

The following links might be helpful in accomplishing this on your server:

If you need further assistance, you may need to reach out to your web host or systems administrator to resolve this.

Curl Error: Couldn't resolve host (6)

A CURL code 6 error indicates an inability for your DNS to resolve the WHMCS licensing server. This could indicate a temporary issue with your DNS provider, or a larger misconfiguration.

If these points have been eliminated, check your Zone files for the presence of an entry for and remove it if found.

Curl Error: Couldn't connect to host (7)

A CURL code 7 error indicates an inability to connect to the WHMCS licensing server. This is typically caused by a firewall configuration. CURL uses port 443 for secure connections, so ensure that connections are permitted on this port.

Curl Error: Connection refused - Code 7

See above.

Curl Error: Problem with the SSL CA cert (path? access rights?) - 77

See Outdated Root CA Bundles

Curl Error: error setting certificate verify locations

See Outdated Root CA Bundles

Outdated Root CA Bundles

The license validation is performed via an SSL connection. This helps to ensure the security and integrity of license checks.

Errors can occur when placing the CURL call using the "curlopt_ssl_verifypeer" function if your server does not have the appropriate root certificate authority (CA) bundles to validate the SSL connection to our licensing server. This can be caused by the CA bundle files being missing or outdated.

Note: This error does not relate to the validity or existence of an SSL certificate on your own website. The CA bundles referred to here are located on the server side at root level.

Frequently updated CA Root Certificates are available from your Operating System's repository or the cURL website at

If you are unsure how to check for these certificates or update them, we recommend that you contact your web host or systems administrator for assistance.

Other Curl Error Codes

Other CURL error codes are detailed in the official documentation at