Can't add Invoice to sales order

I'm writing an api script in php that creates a sales order and invoice when a customer submits an order on our website. The script has no problem making both the invoice and the sales order. But when I goto the sales order's invoice tab, it hasn't added the invoice that I created to the sales order, even though the invoice is listed in the invoices section of Zoho inventory. Does anyone have any idea how to add the invoice to the sales order?

$params ='{
"customer_id": '.$contactsDecode->contacts[0]->contact_id.',
"salesorder_number": '.$lastOrder['Order Number'].',
"date": '.$combinedTime.',
"reference_number": '.$newInvoiceNum.',
"invoices": [
{
"invoice_id": '.$newInvoiceNum.',
"invoice_number": '.$newInvoiceNum.',
"status": "fulfilled",
"total": 350,
"balance": 0
}
],
"line_items": [
'.$item .'
],
"is_emailed": "true",
"delivery_method": "USPS",
"salesorder_id" : '.$lastOrder['Order Number'].',
"customer_name" : "'.$lastOrder['Customer Name'].'"
}';
$invoiceParams ='{
"customer_id": '.$contactsDecode->contacts[0]->contact_id.',
"invoice_number": '.$newInvoiceNum.',
"status": "paid",
"date": '.$combinedTime.',
"reference_number": '.$lastOrder['orderID'].',
"discount": 0,
"line_items": [
'.$item .'
],
"is_discount_before_tax": true,
"discount_type": "item_level",
"is_inclusive_tax": false,
"exchange_rate": 1
}';
$connectionStatus .= $zohoClient->createSalesOrder($params, true);
$connectionStatus .= $zohoClient->createInvoice($invoiceParams, true);

Zoho Desk Resources

Desk Community Learning Series
Digest
Functions
Meetups
Kbase
Resources
Glossary
Desk Marketplace
MVP Corner
Word of the Day

Topic Participants
Carlos Frias

Sticky Posts
Zoho Inventory will discontinue support for older browser versions soon
Hello users, Starting from May 15, 2024, Zoho Inventory will no longer support the following browser versions: Browsers Version Restrictions Firefox Browser Versions older than 100 Google Chrome Versions older than 100 Microsoft Edge Versions older than
Zoho Finance Workshop 2023 is coming to the USA. Meet the experts, get exclusive training on Zoho Finance apps and more.
Hello all, We'd like to invite you to our biggest Zoho Finance workshop in the United States. After a brief break, we are excited to be back. This year, we're bringing together our customers and community members for two days of curated hands-on sessions,
Celebrating our Zoho Community SuperBuds
The SuperBud program recognizes the efforts Zoho users put in to help the rest of the community thrive and grow in their individual Zoho journeys. Be it the ZUG meetups or these forums, several Zoho users including our MVPs andZUG leaders, have stepped
Authtoken Deprecation for Zoho Inventory APIs
UPDATE (7 July 2021): We've extended the deadline to 30 August 2021 for converting Authtokens to OAuth. Hello everyone, The usage of Authtokens to authenticate API calls is being deprecated on 30 August 2021 across Zoho's Finance suite of products,
ZOHO Inventory - Early Access
https://twitter.com/zoho/status/646715717849493504