Add customer to cart with SOAP - View on FE

Question

When I call "shoppingCartProductAdd" it adds the specific customer to the cart and displays it when I call "shoppingCartInfo". However it does not show up in the cart from the customer on the frontend. Is it possible to add a customer to an existing cart (also created with SOAP API) and display it on the frontend? Or is this not the scope from the API?

My SOAP calls:

Creating the shopping cart:

<x:Envelope xmlns:x="http://schemas.xmlsoap.org/soap/envelope/" xmlns:urn="urn:Magento">
    <x:Header/>
    <x:Body>
        <urn:shoppingCartCreate>
            <urn:sessionId>{sessionId}</urn:sessionId>
            <urn:storeId>1</urn:storeId>
        </urn:shoppingCartCreate>
    </x:Body>
</x:Envelope>

Adding a product to the cart

<x:Envelope xmlns:x="http://schemas.xmlsoap.org/soap/envelope/" xmlns:urn="urn:Magento">
<x:Header/>
<x:Body>
    <urn:shoppingCartProductAdd>
        <urn:sessionId>{sessionId}</urn:sessionId>
        <urn:quoteId>682</urn:quoteId>
        <products>
            <product>
                <sku>testproduct</sku>
                <qty>1</qty>
            </product>
       </products>
       <urn:storeId>1</urn:storeId>
   </urn:shoppingCartProductAdd>
</x:Body>

Set the customer from the cart

<x:Envelope xmlns:x="http://schemas.xmlsoap.org/soap/envelope/" xmlns:urn="urn:Magento">
    <x:Header/>
    <x:Body>
    <urn:shoppingCartCustomerSet>
        <urn:sessionId>{sessionId}</urn:sessionId>
        <urn:quoteId>682</urn:quoteId>
        <customer>
            <mode>guest</mode>
            <firstname>firstname</firstname>
            <lastname>lastname</lastname>
            <email>[email protected]</email>
            <customer_id>137</customer_id>
        </customer>
    </urn:shoppingCartCustomerSet>
</x:Body>

Answer 1

Turned out the cart/quote is not active when adding it via SOAP API.