try to use console button

app/UI/Vms/Buttons/ConsoleButton.php

@@ -31,11 +31,9 @@ class ConsoleButton extends ButtonDataTableModalAction implements ClientArea
 
     public function initContent()
     {
-        $redirectButton = new RedirectButton('novnc');
-        $redirectButton->setImageUrl(BuildUrl::getAppAssetsURL() . DS . 'img' . DS . 'buttons' . DS . 'novnc.png');
-        $redirectButton->setHref("#");
-        $redirectButton->setIcon('lu-zmdi lu-zmdi-fullscreen');
-        $this->addButton($redirectButton);
+        $this->setImageUrl(BuildUrl::getAppAssetsURL() . DS . 'img' . DS . 'buttons' . DS . 'novnc.png');
+        $this->setHref("#");
+        $this->setIcon('lu-zmdi lu-zmdi-fullscreen');
         $this->initIds('consoleButton');
         $this->setDisableByColumnValue("vmid", 0);
     }