How to insert custom code into main-product.liquid using API on app?

Store Design
1

We are using below code to include custom liquid file on main-product.liquid, it is not inserting. But the same code works for product.liquid. How to make it work for main-product.liquid?

We are testing on two different stores having product.liquid and main-product.liquid

$productData = [ ‘asset’ => [ ‘key’ => ‘templates/main-product.liquid’ ] ];

$productPageData = $shop->api()->rest(‘GET’, ‘/admin/themes/’.$activeThemeId.‘/assets.json’, $productData)[‘body’][‘container’][‘asset’][‘value’];

$productPageData = $productPageData.“\n{% include ‘custom-product-btn’ %}”;

$productPageContent = [ ‘asset’ => [ ‘key’ => ‘templates/main-product.liquid’, ‘value’ => $productPageData ] ];

$shop->api()->rest(‘PUT’, ‘/admin/themes/’.$activeThemeId.‘/assets.json’, $productPageContent);

$shopdata = Customize::where(‘storeName’, $shopName)->first();
$shopdata->appIntegrated = ‘1’;
$shopdata->save();