@Belal Hany 
Assuming that you’ve technically set everything right between Shopify and Klaviyo, there’s one, most common reason that’s might be causing your problem. That’s the Double Opt-In process. If you have a Double Opt-In enabled for your “Newsletter” list, after someone subscribes, they will receive an email to confirm that they want to subscribe for newsletter.
At this point they’re added to the Profiles section, but since they still haven’t confirmed subscription via email, they won’t be added to your “Newsletter” list.
After they confirm their email, they will automatically be placed to the List.

You can test to see if this is your case by subscribing to your form, and see if you’ll receive the “Confirmation Email”. If you do receive it, and after confirming you get subscribed to your “Newsletter” list, than you need to disable Double Opt-In for that List if you want to skip the confirmation email and place subscribers directly into the list after they subscribe.

Here are more details about Double Opt-In process:

The Double Opt-in feature in Klaviyo is hidden from the settings by default for free plan. If you are on a paid plan in Klaviyo, you can submit a request to enable this option for your account here: Klaviyo Contact Form.

Ask Klaviyo support team to reveal that option for you, so you can toggle Double Opt-in on and off for each of your lists.

After you get a confirmation that the option is enabled for your account, navigate to the List for which you want to turn off the Double Opt-in. Open the list and click on “Settings”. Uncheck the “Require subscribers to confirm their subscription before being added to your list.” option.
 

After you uncheck this option, Klaviyo will stop sending the Double Opt-in Emails to the subscribers joining that List.

Here is the documentation from Klaviyo on Double Opt-in: The Double Opt-In Process

Hope this helps!

@Belal Hany 
Assuming that you’ve technically set everything right between Shopify and Klaviyo, there’s one, most common reason that’s might be causing your problem. That’s the Double Opt-In process. If you have a Double Opt-In enabled for your “Newsletter” list, after someone subscribes, they will receive an email to confirm that they want to subscribe for newsletter.
At this point they’re added to the Profiles section, but since they still haven’t confirmed subscription via email, they won’t be added to your “Newsletter” list.
After they confirm their email, they will automatically be placed to the List.

You can test to see if this is your case by subscribing to your form, and see if you’ll receive the “Confirmation Email”. If you do receive it, and after confirming you get subscribed to your “Newsletter” list, than you need to disable Double Opt-In for that List if you want to skip the confirmation email and place subscribers directly into the list after they subscribe.

Here are more details about Double Opt-In process:

The Double Opt-in feature in Klaviyo is hidden from the settings by default for free plan. If you are on a paid plan in Klaviyo, you can submit a request to enable this option for your account here: Klaviyo Contact Form.

Ask Klaviyo support team to reveal that option for you, so you can toggle Double Opt-in on and off for each of your lists.

After you get a confirmation that the option is enabled for your account, navigate to the List for which you want to turn off the Double Opt-in. Open the list and click on “Settings”. Uncheck the “Require subscribers to confirm their subscription before being added to your list.” option.
 

 

After you uncheck this option, Klaviyo will stop sending the Double Opt-in Emails to the subscribers joining that List.

Here is the documentation from Klaviyo on Double Opt-in: The Double Opt-In Process

Hope this helps!

there is no confirmation email. Even if I check the profile it says “accepts marketing: yes”

image of my settings

@Belal Hany - Have you checked Spam folder for the confirmation Email?

The only other situation where people that are coming from Shopify to Klaviyo, with “Accepts Marketing = True”, but they’re not placed in a List, is if those people started checkout but haven’t purchased.
When someone initiate the checkout phase, they will immediately sync with Klaviyo, but remain only in the Profiles section until they finish the purchase.

These are the most common situations that can cause the problem you’re having. If it’s neither of these, I suggest hiring an expert to check the entire Klaviyo and Shopify setup to figure out the problem.

Is it possible to make an automation that puts a profile in a list when there’s a new profile with “Accepts Marketing = True”? I guess that would solve the issue, right?

@vitbarreto I believe that could be one solution, but in this instance, the OP was having issues with getting any of the confirmation emails for subscribing. It’s likely due to Double Opt In, and the emails for test accounts may have gone into promotional or a different inbox. Unless there is something else at play or if the integration isn’y syncing properly, @retention’s solution is right on point. 

@Belal Hany were you able to solve your issue from the comments above? I’m having the exact same issue and at a loss of how to resolve it. I’ve even watched the academy courses and they don’t go into lists at all, just a quick mention of them.

A few points to add:

• You can only belong/subscribe to the List once (unless you unsubscribe, or your profile is deleted).  So if you are just testing it with the same email address over and over, you won’t get subsequent “Confirmation” emails.
• Make sure in the Integration → Shopify, you set the List that you expect people to belong to when they “Accept Marketing” in Shoipfy.
• Shopify has it’s own way of collecting “Customers” via it’s native forms and through the Checkout Opt-In, etc.  In some cases, you may have “Double Opt-In” enabled on Shopify too - so Shopify is waiting for user confirmation before it passes it to Klaviyo.  Make sure your know the system that’s actually collecting the emails (Shopify, Klaviyo Signup Forms, or maybe a 3rd party email capture system?) 

@mariahpeters not sure if you saw the additional notes from Joseph above, but his comment about testing with the same email is actually a common one for Klaviyo customers to encounter, so that is definitely a good one to look out for if you are seeing some similar issues.