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supportHi, ever since a website has been migrated, the signup form via Ninja Forms hasn’t worked. The error in the logs is: 2026-07-01 12:01:50: 400: The resource submitted could not be validated. For field-specific details, see the ‘errors’ array. – ({“type”:” https://mailchimp.com/developer/marketing/docs/errors/” ;,”title”:”Invalid Resource”,”status”:400,”detail”:”The resource submitted could not be validated. For field-specific details, see the ‘errors’ array.”,”instance”:”…”,”errors”:[{“field”:”ip_signup”,”message”:”This value is not a valid IP. Valid IPs have a format of W.X.Y.Z where each letter represents a number between 0-255.”}]}) Please can you advise how to fix this?
Hello @pixelshrink 👋🏽, This issue is usually caused by browsers’ inability to access the user’s IP address (mainly on Safari or MacOs), which Mailchimp requires for spam protection. You can ask the user to try another browser/device or you can skip sending the IP data to Mailchimp. If you want to skip sending the IP data to Mailchimp, please add the code snippet below to your active theme’s function.php file or via the Code Snippets plugin. /** Stop sending subscribers IP address during mailchimp optin subscription */ add_filter('mo_connections_mailchimp_subscription_parameters', function ($parameters) { unset($parameters['ip_signup']); return $parameters; }); Please note that Mailchimp uses IP addresses to detect bot submissions. If a user’s browser can’t read their IP address, the submission fails the bot test, and the error is logged. If you skip sending the IP data to Mailchimp, you might see an increase in spam. Cheers
Great, thanks. It’s a website that’s being run through Cloudflare so would it be that that is the problem with the IP address? If so is there a workaround or will we still need to switch off IP address submissions? This happened on Windows so it’s not a Mac issue.
Yes, Cloudflare is very likely the cause here. Mailchimp’s ip_signup field only accepts IPv4 addresses, and Cloudflare serves and forwards traffic over IPv6 by default, so the IPv6 address sent to Mailchimp is rejected, causing this issue. The filter I shared above will fix this for now. We’ve also updated the integration so that, in our next release, MailOptin will no longer send IPv6 addresses to Mailchimp’s ip_signup field. I’ll let you know once that update is available so you can remove the filter and benefit from Mailchimp’s spam protection for IPv4 users. Best regards
Hello @pixelshrink 👋🏽, This issue is usually caused by browsers’ inability to access the user’s IP address (mainly on Safari or MacOs), which Mailchimp requires for spam protection. You can ask the user to try another browser/device or you can skip sending the IP data to Mailchimp. If you want to skip sending the IP data to Mailchimp, please add the code snippet below to your active theme’s function.php file or via the Code Snippets plugin. /** Stop sending subscribers IP address during mailchimp optin subscription */ add_filter('mo_connections_mailchimp_subscription_parameters', function ($parameters) { unset($parameters['ip_signup']); return $parameters; }); Please note that Mailchimp uses IP addresses to detect bot submissions. If a user’s browser can’t read their IP address, the submission fails the bot test, and the error is logged. If you skip sending the IP data to Mailchimp, you might see an increase in spam. Cheers
Great, thanks. It’s a website that’s being run through Cloudflare so would it be that that is the problem with the IP address? If so is there a workaround or will we still need to switch off IP address submissions? This happened on Windows so it’s not a Mac issue.
Yes, Cloudflare is very likely the cause here. Mailchimp’s ip_signup field only accepts IPv4 addresses, and Cloudflare serves and forwards traffic over IPv6 by default, so the IPv6 address sent to Mailchimp is rejected, causing this issue. The filter I shared above will fix this for now. We’ve also updated the integration so that, in our next release, MailOptin will no longer send IPv6 addresses to Mailchimp’s ip_signup field. I’ll let you know once that update is available so you can remove the filter and benefit from Mailchimp’s spam protection for IPv4 users. Best regards