Unable to find install new plugin

Just working and testing a new 3.3.1 version to see if I will upload an ‘old’ 3.0.9. (also on a new server)
But I dont see and find how show, the plugin button to add new plugin.

The dir in config is right, i just see correct editor and all seems work correctly. What I have to check ?
php 5.4 debian 7
define(‘PLUGIN_ROOTDIR’, ‘plugins’);

@demoweb If the install button is not displayed then your server must be missing a php extension.

There should be an explanatory message at the top of the page.

thx, I thought was not important. I just setup manually…thx for reply and support