Payments via AmazonPay fails

Hi,
AmazonPay has worked on our webshop vry well, but after the succesful update from AmazonPay it fails.
I got these errormessages:

[10-Jun-2021 09:39:30 UTC] kSiaVp – WC_Gateway_Amazon_Payments_Advanced::handle_return – Error: Order could not be found. Checkout Session ID: xxxxx.
[10-Jun-2021 09:39:31 UTC] SoqNsb – WC_Amazon_Payments_Advanced_IPN_Handler::check_ipn_request – Received IPN request.
[10-Jun-2021 09:39:31 UTC] PHP Warning: file_get_contents(): https:// wrapper is disabled in the server configuration by allow_url_fopen=0 in /var/www/xxxx/html/yyyy/wp-content/plugins/woocommerce-gateway-amazon-payments-advanced/includes/class-wc-amazon-payments-advanced-ipn-handler.php on line 145
[10-Jun-2021 09:39:31 UTC] PHP Warning: file_get_contents(https://sns.eu-west-1.amazonaws.com/SimpleNotificationService-xxxxxxx.pem): failed to open stream: no suitable wrapper could be found in /var/www/xxxxxx/html/xxxxx/wp-content/plugins/woocommerce-gateway-amazon-payments-advanced/includes/class-wc-amazon-payments-advanced-ipn-handler.php on line 145
[10-Jun-2021 09:39:31 UTC] SoqNsb – WC_Amazon_Payments_Advanced_IPN_Handler::check_ipn_request – Failed to handle IPN request: Cannot get the public key from the certificate.

as workaround I’ve activated allow_url_fopen, but it seems not to be a good and safe solution. Before the update it was not nessesary.

What can I do?