Signup popup displays correctly, but form submission doesn’t subscribe users or send confirmation email

Description

Hi everyone,

I’m trying to set up a signup popup in Klaviyo with the following goals:

• Show a signup popup on my website

• When a user clicks Sign Up, send them a confirmation email (double opt-in)

• Ensure that each email address can only receive one discount code

At the moment, I’m running into an issue where the popup displays correctly on the website, but after clicking “Sign Up,” the subscription doesn’t seem to complete.

Here’s what’s happening:

• The popup appears as expected on the site

• The user enters an email and clicks the signup button

• However, the email address does not appear to be subscribed to the list

• I also don’t receive any confirmation email, so I can’t tell whether the double opt-in is working or not

What I’ve already checked:

• The signup button action is set to Submit form

• The form is set to Subscribe to a List

• I am testing with a new email address that has not subscribed before

• The popup is built using Klaviyo’s native signup form (not a custom embedded form)

My questions are:

1. What are the most common reasons a Klaviyo signup popup would display but not successfully subscribe users?

2. Is there a reliable way to test whether the confirmation (double opt-in) email is being sent?

3. Are there any specific list or consent settings I should double-check to make sure the subscription and confirmation email are triggered correctly?

Any guidance or troubleshooting steps would be greatly appreciated.
Thank you in advance!