I am experiencing an issue where the parent order fails (due to the Woocommerce Stripe Gateway, the customer payment fails and then is resolved, updating the parent order status to Processing) but the sub-order remains failed. Due to this, the vendor believes the order has failed and does not ship, however the customer has been charged.
May I know if you have checked marketplace plugin with WooCommerce and standard theme (storefront/twenty). Please deactivate all your plugin, except WooCommerce and WCMp + addon. You can then check the flow. If everything is working fine, in order to detect which plugin is causing conflict- please activate each plugin consecutively and check the flow.
Similarly, for theme conflict- please deactivate the current theme and check with standard WooCommerce theme (storefront/twenty) It is suggested to please perform these tests on your staging website and keep us posted with the outcome.