Order status remains on processing

Hi all,

All orders (live ones and test ones) get stuck on the status ‘processing’ and it does not move on to ‘completed’. As a result my customers also do not get their confirmation email. Only when I manually update the status to ‘completed’. This used to be working fine last year when I used the Mollie plugin.

I have checked our the Mollie logs and all seems to be fine. For example, logs from the last test order:

2019-01-22T19:31:11+00:00 DEBUG mollie_wc_gateway_creditcard: Start process_payment for order 3532
2019-01-22T19:31:11+00:00 DEBUG getUserMollieCustomerId: Mollie Customer ID (cst_2huneyxha4) found and valid for user 1 on this API key. (test).
2019-01-22T19:31:11+00:00 DEBUG mollie_wc_gateway_creditcard: Order 3532 webhookUrl: https://adtribes.io/wc-api/mollie_wc_gateway_creditcard/?order_id=3532&key=wc_order_kHIBenyFdILdY
2019-01-22T19:31:11+00:00 DEBUG mollie_wc_gateway_creditcard: Create Mollie payment object for order 3532
2019-01-22T19:31:11+00:00 DEBUG Creating payment object: type Order, first try creating a Mollie Order.
2019-01-22T19:31:11+00:00 DEBUG mollie_wc_gateway_creditcard: Mollie payment object ord_9vq2h (test) created for order 3532
2019-01-22T19:31:11+00:00 DEBUG For order 3532 redirect user to Mollie Checkout URL: https://www.mollie.com/payscreen/order/checkout/9vq2h
2019-01-22T19:31:20+00:00 DEBUG mollie_wc_gateway_creditcard: Mollie payment object ord_9vq2h (test) webhook call for order 3532.
2019-01-22T19:31:20+00:00 DEBUG mollie_wc_gateway_creditcard: Order 3532 orderNeedsPayment check: yes, order not previously processed by Mollie gateway.
2019-01-22T19:31:20+00:00 DEBUG Mollie_WC_Payment_Order::onWebhookPaid called for order 3532
2019-01-22T19:31:25+00:00 DEBUG Mollie_WC_Payment_Order::onWebhookPaid WooCommerce payment_complete() processed and returned to Mollie_WC_Payment_Order::onWebhookPaid for order 3532
2019-01-22T19:31:25+00:00 DEBUG Mollie_WC_Payment_Order::onWebhookPaid processing paid order via Mollie plugin fully completed for order 3532
2019-01-22T19:31:29+00:00 DEBUG Mollie_WC_Gateway_Abstract::getReturnRedirectUrlForOrder 3532: Determine what the redirect URL in WooCommerce should be.
2019-01-22T19:31:29+00:00 DEBUG Mollie_WC_Plugin::onMollieReturn: Redirect url on return order mollie_wc_gateway_creditcard, order 3532: https://adtribes.io/checkout/order-received/3532/?key=wc_order_kHIBenyFdILdY&utm_nooverride=1

What could be causing this and how do I fix this?

Thanks!
Eva