Mailchimp email form TypeError: undefined is not a function js error

We have been using a mailchimp email form for visitors to sign up to a mailing list. We just added groups so we can segment the audience by interest. Now when the form is submitted the following error occurs “TypeError: undefined is not a function”.

Our theme and cornerstone is up to date.

Can you please advise.


Hello @spaghettiweb,

Thanks for writing in.

I tried to test the form and I am getting this JS error:

Since this is a Javascript error, this might be caused a third party plugin conflict so please try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.

If the issue persists, please provide us with the admin access to your site in a Secure Note:

Thanks for the reply. We saw the same js error. Disabling all 3rd party plugins did not resolve the issue. The form previously worked fine with this exact configuration. Please see secure note with admin login details.

Hello @spaghettiweb,

I have uploaded the unreleased version of the Email Forms 2.0.4. What needs to be done now is for you to update your X and Cornerstone to X 6.5.6 and Cornerstone 3.5.5.

Please let us know how it goes.


Thanks for the assistance. We were unaware that there was a manual update for X and cornerstone. We have now updated to version 6.5.6 and 3.5.5 respectively. The form now submits and displays the success message. The issue is resolved. Thank you.

You’re welcome, @spaghettiweb. We’re glad the issue was resolved.

I have same JS error and would like to update Email Forms to 2.0.4. if that was the OP’s solution.

I am running X 6.5.6 and CS 3.5.5. and wordpress 5.2.3

People have been posting about this error since Nov 2018??? Its now Sep 2019! Email Forms is a Themeco plugin is it not?

You’ll need Email Forms 2.04. We had the same error on another site after this one was resolved. We copied the latest Email Forms plugin over to the other site as well and it worked fine. Not sure why the update hasn’t been released yet…?

Hey @blueoaks,

You can download the unreleased and patched update of Email Forms from here:

We are waiting for our developers for the final release along with the latest X theme.
It will be available in the automatic updates soon.

Best Regards.

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