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How to Fix cURL Error 6 When Activating a License Key ​

This article covers how to resolve a cURL error 6 ("Could not resolve host api.themeisle.com") that appears when trying to activate a Themeisle license key, caused by a server-side firewall, DNS, or security-plugin block.

cURL error 6: Could not resolve host ​

cURL error 6 means your server was unable to resolve the hostname api.themeisle.com via DNS. This is a server-side connectivity issue, not a problem with the license key itself.

Common causes:

  • A server firewall or hosting restriction is blocking outbound HTTPS requests to external domains.
  • A security plugin (e.g., Wordfence, iThemes Security) is blocking the outbound connection.
  • A DNS misconfiguration on the server is preventing name resolution.

Steps to fix:

1. Whitelist api.themeisle.com in your security plugin. If you are using Wordfence, iThemes Security, or a similar plugin, check its firewall or blocked requests settings and add api.themeisle.com to the allowlist.

2. Check your hosting firewall. Some managed hosting providers block outbound HTTP/HTTPS requests by default. Log in to your hosting control panel and verify that outbound connections to external domains are permitted, or contact your host's support team and ask them to allow outbound HTTPS traffic to api.themeisle.com.

3. Check your site's error log. In your hosting control panel or via FTP, open the PHP/server error log and look for entries mentioning cURL error 6 or api.themeisle.com. This can confirm whether the issue is DNS- or firewall-related.

4. Test connectivity from the server. If you have SSH access, run the following command to confirm the server can reach the license endpoint:

bash
curl -I https://api.themeisle.com

A successful response returns HTTP headers. If you see Could not resolve host or a connection timeout, the block is confirmed at the server level.

5. Contact your host. If the above steps do not resolve the issue, share the error message with your hosting provider and ask them to allow outbound HTTPS requests to api.themeisle.com on port 443.

📝 Note: This error only affects the license activation request. Your site and the plugin itself continue to work normally while you troubleshoot the connection.

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