Klaviyo: Email Marketing & SMS

Klaviyo customer support reply to my request after 24hrs. Why is my Welcome Series not sending? I have checked my Signup Forms tab and Enabled Integrations they are matching. Please note: Additionally, your account is on our free tier, so by default it will have Double Opt In. This feature requires anyone that signs up to receive a confirmation email which they must accept before they will be added to the newsletter and welcome flow. It is not uncommon for the confirmation email to be missed. I hope this can help someone who are not familiar with Double Opt In. Thank you Ian Nichols