I found the problem for me: there is an error in the url i used.
I accessed the Settings page from the Installed plugins page.
There the set url is: /wp-admin/admin.php?page=woocommerce_settings&tab=integration§ion=google-merchant-center
But the correct way to access the plugin settings is by going to WooCommerce > Settings > “INtegrations” tab > “Google Merchant Center”.
The correct direct url is: /wp-admin/admin.php?page=wc-settings&tab=integration§ion=google-merchant-center
From there you’ll can setup the plugin.
Hope this will help,
Adamo “Aerendir”