rder_submit.tracing_error :: Method Not Allowed

Hello,
I need your help regarding order sync with MailChimp.
Basic information:
1. The shop is connected to MailChimp via API key and is noted as Connected on the MailChimp dashboard
2. The latest version of the plugin is installed in the shop
3. On MailChimp’s API Keys site there is a number of request from the last 24 hours like so:

Date/Time Result Throttled? Source IP Method Format Exec Time User Agent Ver Response
2018-12-10 17:53:16 GMT nope 79.96.228.61 GET /lists/ php 0.192s MailChimp for WooCommerce/2.1.11; PHP/7.1.15; WordPress/4.9.8; Woo/; 3.0 n/a

4. No order is synced from the beginning of the store integration. Under the debug log there is a number of errors like this one:

2018-12-10T12:50:46+00:00 DEBUG order_submit :: ##259 :: Array
(
[id] => #259
[customer] => Array
(
[id] => 8b4a063b53d39f695b15f11ff3b01b10
[email_address] => a.waszynska@interia.pl
[opt_in_status] => 1
[company] => Beyond Strategy
[first_name] => Sara
[last_name] => Waszyńska
[orders_count] => 1
[total_spent] => 147
[address] => Array
(
[name] => Sara Waszyńska
[address1] => Główna
[address2] => 130
[city] => Krzyszkowo
[postal_code] => 62-090
[country] => PL
[phone] => 727931028
)

)

[financial_status] => cancelled
[currency_code] => PLN
[order_total] => 154
[order_url] => https://krenigconsulting.pl/moje-konto/view-order/2617/
[tax_total] => 28.79
[discount_total] => 0
[shipping_total] => 12.2
[processed_at_foreign] => 2018-12-03 21:49:09
[cancelled_at_foreign] => 2018-12-10 12:46:20
[shipping_address] => Array
(
[name] => Sara Waszyńska
[address1] => Główna
[address2] => 130
[city] => Krzyszkowo
[postal_code] => 62-090
[country] => PL
[phone] => 727931028
)

[billing_address] => Array
(
[name] => Sara Waszyńska
[address1] => Główna
[address2] => 130
[city] => Krzyszkowo
[postal_code] => 62-090
[country] => PL
[phone] => 727931028
)

[lines] => Array
(
[0] => Array
(
[id] => 878
[product_id] => 2534
[product_variant_id] => 2534
[quantity] => 1
[price] => 113.00813
)

)

)

2018-12-10T12:50:47+00:00 ERROR order_submit.tracing_error :: Method Not Allowed :: The requested method and resource are not compatible. See the Allow header for this resource’s available methods. on 1470 in /wp-content/plugins/mailchimp-for-woocommerce/includes/api/class-mailchimp-api.php

Please help.
Jacek

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