update a web part property using powershell

Try using below code

 $List = $context.Web.Lists.GetByTitle("ListName")
        $context.Load($List)
        $context.ExecuteQuery()


        $Pages = $List.RootFolder.Files
        $context.Load($Pages)
        $context.ExecuteQuery()

        $Page = $Pages | Where {$_.Name -eq "ViewName"}
        $context.Load($Page)
        $context.ExecuteQuery()


        $WPM       = $Page.GetLimitedWebPartManager("Shared")
        $context.Load($WPM)
        $context.ExecuteQuery()

        $WebParts = $WPM.WebParts
        $context.Load($WebParts)
        $context.ExecuteQuery()

        $WebPart = $WebParts[0]
        $context.Load($WebPart)
        $context.ExecuteQuery()

        $WebPart.WebPart.Properties["AuthorizationFilter"] = "My Group"

        $WebPart.SaveWebPartChanges();
        $context.Load($WebPart);
        $context.ExecuteQuery();

RefClick Here