Hello, by default the plugin should return you straight to the “Thank you” page of the website upon purchase completion.
Have you modified the return urn at all and while using the test credentials have you also tapped on the “test mode” checkbox in the settings?
IF you want to provide a link to the Woocommerce status report (Woocommerce -> status) it might also provide some insight into the possible cause.
The plugin is fully WPML compatible
