Thank you for the support.
Everything now worked as it should. Only errors became visible when ordering the gift card and when redeeming the gift card.
[17-Feb-2022 08:22:57 UTC] PHP Warning: Undefined array key "query" in /home/u69913p99999/domains/website.nl/public_html/wp-content/plugins/mollie-payments-for-woocommerce/src/Mollie/WC/Gateway/Abstract.php on line 2691
[17-Feb-2022 08:23:07 UTC] PHP Deprecated: get_used_coupons is <strong>verouderd</strong> sinds versie 3.7. Gebruik in plaats daarvan WC_Abstract_Order::get_coupon_codes. in /home/u69913p99999/domains/website.nl/public_html/wp-includes/functions.php on line 5316
[17-Feb-2022 08:29:07 UTC] PHP Warning: Undefined array key "query" in /home/u69913p99999/domains/website.nl/public_html/wp-content/plugins/mollie-payments-for-woocommerce/src/Mollie/WC/Gateway/Abstract.php on line 2691
[17-Feb-2022 08:29:07 UTC] PHP Warning: Undefined array key "query" in /home/u69913p99999/domains/website.nl/public_html/wp-content/plugins/mollie-payments-for-woocommerce/src/Mollie/WC/Gateway/Abstract.php on line 2691
[17-Feb-2022 08:29:19 UTC] PHP Deprecated: get_used_coupons is <strong>verouderd</strong> sinds versie 3.7. Gebruik in plaats daarvan WC_Abstract_Order::get_coupon_codes. in /home/u69913p99999/domains/website.nl/public_html/wp-includes/functions.php on line 5316
