Payment issues with second language

Hello

Doing an order and payment with the default (English) language is working without any problems, in the "mailchimp_woocommerce_landing_site" custom field I get this:

https://chilli-cycling.asia/?wc-api=omise_callback&order_id=5573&token=13e7ed80f4955f4d7895c0acc2a130fc945f9ab08255af83ce37a7c78c1fcb9a

But when having in the second language (German / de) I get in this custom field "https://chilli-cycling.asia/de//de/zur-kasse/order-received/5568/?key=wc_order_itTE42Bchc08O"

And I am not able to pay for it.

In the mailchimp log I see this:

--- start ---
19T09:06:15+00:00 ERROR order_submit.error :: addStoreOrder :: #5568 :: Error Code 400 ::

: Required fields were not provided: lines on 2426 in /mnt/disk1/home/chillicyclingksb/public_html/wp-content/plugins/mailchimp-for-woocommerce/includes/api/class-mailchimp-api.php
2023-01-19T09:06:17+00:00 NOTICE order_submit :: #5567 has a financial status of pending and was skipped.
2023-01-19T09:06:18+00:00 NOTICE action_scheduler.queue_job :: MailChimp_WooCommerce_Single_Order starts in 90 seconds :: obj_id 5570
2023-01-19T09:06:27+00:00 NOTICE debug :: Order ID 5571 was pending and is now completed :: Array
(
[new_order] => 1
[tracking] => Array
(
[campaign_id] =>
[landing_site] => https://chilli-cycling.asia/de//de/zur-kasse/order-received/5568/?key=wc_order_itTE42Bchc08O
)

)

2023-01-19T09:06:27+00:00 NOTICE action_scheduler.queue_job :: MailChimp_WooCommerce_Single_Order starts in 90 seconds :: obj_id 5571
2023-01-19T09:08:48+00:00 NOTICE order_submit :: #5570 has a financial status of pending and was skipped.
2023-01-19T09:08:52+00:00 ERROR order_submit.error :: addStoreOrder :: #5571 :: Error Code 400 ::

: Required fields were not provided: lines on 2426 in /mnt/disk1/home/chillicyclingksb/public_html/wp-content/plugins/mailchimp-for-woocommerce/includes/api/class-mailchimp-api.php

--- end ---

What could be the problem?

Regards,

Simon

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