I have a site that had the Envato Toolkit plugin installed.
I saw a message “Warning: The Envato Toolkit plugin is no longer supported and will stop functioning very shortly. Please delete the Envato Toolkit plugin and install the Envato Market plugin. Click here for more details.”
So I uninstalled Envato Toolkit, and installed and activated Envato Market, but the message is still there at the top of the Dashboard.
I have given you the right procedure that envato suggest.
at first you have to uninstalled the Envato Toolkit plugin then have to delete the plugin from your WordPress website then have to Install the new Envato Market plugin.
If you have done according to the above way then you can contact envato customer support to get help from their side.