If you want to use Shopify’s Cart Panel follow these steps:
To install and configure the Headless app:
>> From Cart Behaviour select “Add to Cart (Open cart drawer)”

>> From “Enable Native Cart Drawer” Notification, select the “install headless by Shopify” button. This is a Shopify-built App, and it is free of cost; you will not be charged.

>> It will redirect you to the page where you can install the Headless app.

>> After installing click “Create Storefront”

>> From the “Manage API Access” section click on “Manage” button beside “Storefront API”.

>> Then from “Public Access Token” copy the following code:

>> Go back to the ShopComponent’s admin panel where you have created the component, and below the “Public Access Token” field, paste the code and click on “Verify”.

All done, your customers will now see the add to cart button.