Did you try disabling double opt in for your Klaviyo list?

Yep still doesn't properly opt them in.  see image. Using Zaps for now but I’d rather not. Seems so unnecessary!

It does take the email, share it with Klaviyo, adds them to a list, I CAN email them, but there is an alert saying they are not properly subscribed to receive emails.  

Check your Klaviyo settings, specifically the settings for the list you're adding users to.

Make sure that Single Opt In is set (and not double opt in like the picture). This usually solves it for me.

I have the same issue, and I have Single opt-in. 

Did you solve it?

It’s an API issue.

See answer from ManyChat.

Klaviyo is currently deprecating its old API and transitioning to the new one. Unfortunately, these changes have affected our integration, as it doesn't support the new Klaviyo API yet. 

Our developers are already aware of the issue, and we are working on updating our integration. Sadly, for now, there's no ETA for the delivery of the fix.  

As a workaround, you may connect to Klavio directly through API using the External Request feature or third-party services such as Zapier or Make. 

That’s a bummer!

If anyone needs help integrating this via API or Zapier/Make feel free to reach out.

Hey man I just ditched doing my “forms” to gather info and subs in many chat.  I simply send the link to my Klaviyo  form embedded on my website.