hello team, first of all thanks for your answer so quickly, i was on holidays, i come back now.
i have done step by step about what you ask me to do, and there are the result .
With all plugin in page vendor product list, i have this picture : errorvendorwithallplugin.jpg
When i disable all of plugin except Woocommerce and WC Marketplace i have this picture : errorvendorwithoutplugin.jpg
so we have the name vendor in this page.
When i switch some default theme i have this picture :errorvendorwithothertheme.jpg