That might be a conflict with your theme. Can you temporarily switch to a default WordPress theme and test again.
Another possible solution is to use the iframe version of the Subscription form inside a Text widget.
Getting the same results by putting it in an iframe text box.
Hey, can you paste a link to a page with the form?
I just published it again on the bottom of the page at http://offkilter.net
Thanks for URL of your website.
May we suggest you to create another form and insert it again. Looks like this one have a specific problem going on. Make sure to assign a list to it. In case it didn’t work, create a new Subscriber List and assign it to this newly created form.
Let us know if that solves the issue.
I just created a new form and still getting the same behavior.
Please get in touch with us here: https://support.mailpoet.com/wordpress-forums/
and use the word: subscription on the ISSUE CODE field.