fix express button not rendered on single product page

Author: alexiglesias31

includes/class-wc-gateway-amazon-payments-advanced-abstract.php

@@ -939,7 +939,7 @@ public function checkout_button( $echo = true, $elem = 'div', $id = 'pay_with_am
 		$subscriptions_enabled   = empty( $this->settings['subscriptions_enabled'] ) || 'yes' === $this->settings['subscriptions_enabled'];
 		$cart_contains_sub       = class_exists( 'WC_Subscriptions_Cart' ) ? WC_Subscriptions_Cart::cart_contains_subscription() : false;
 
-		if ( $subscriptions_installed && ! $subscriptions_enabled && $cart_contains_sub ) {
+		if ( $subscriptions_installed && ! $subscriptions_enabled && $cart_contains_sub && ! is_product() ) {
 			return;
 		}
 

includes/class-wc-gateway-amazon-payments-advanced-subscriptions.php

@@ -19,14 +19,14 @@ public function __construct() {
 
 		add_filter( 'woocommerce_amazon_pa_form_fields_before_legacy', array( $this, 'add_enable_subscriptions_field' ) );
 
+		add_filter( 'woocommerce_amazon_pa_supports', array( $this, 'add_subscription_support' ) );
+
 		if ( 'yes' !== WC_Amazon_Payments_Advanced_API::get_settings( 'subscriptions_enabled' ) ) {
 			return;
 		}
 
 		add_action( 'wp_loaded', array( $this, 'init_handlers' ), 12 );
 
-		add_filter( 'woocommerce_amazon_pa_supports', array( $this, 'add_subscription_support' ) );
-
 		// WC Subscription Hook.
 		add_filter( 'woocommerce_subscriptions_process_payment_for_change_method_via_pay_shortcode', array( $this, 'filter_payment_method_changed_result' ), 10, 2 );
 	}

includes/class-wc-gateway-amazon-payments-advanced.php

@@ -111,6 +111,10 @@ protected function get_availability() {
 			return false;
 		}
 
+		if ( ! $this->possible_subscription_cart_supported() ) {
+			return false;
+		}
+
 		return true;
 	}