It seems there’s a conflict on your site. Do you have any other error messages on the console? Could you please try to reproduce the issue on one of the WordPress’ stock themes (like Twenty Sixteen) with other plugins deactivated? If it disappears, then you can activate the theme and plugins one by one to see which one causes the issue.
Also, could you please make sure that you have
acf_form_head() set correctly? This page should give you more idea about it: https://www.advancedcustomfields.com/resources/create-a-front-end-form/.
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