Polycom VVX screen saver

Hi,

I'm trying to set a screen saver on my VVX 500 by changing the mac.cfg file from the server, but for some reason nothing changes in the phone once that I enter the config. Here's the content of my mac.cfg:

<ucs>
<mb>
<mb.idleDisplay.home mb.idleDisplay.home="https://www.8x8.co.uk/images/8x8-logo-new.png?1464273895" />
<mb.idleDisplay.refresh mb.idleDisplay.refresh="40" />
</mb>
<up>
<up.idleBrowser.enabled up.idleBrowser.enabled="1" />
<up.screenSaver.enabled up.screenSaver.enabled="1" />
<up.screenSaver.type up.screenSaver.type="2" />
<up.screenSaver.waitTime up.screenSaver.waitTime="1" />
</up>
</ucs>

I've been able to change the screen saver from the phone GUI, but I need to be able to do push it from the server as well for a customer. Does somebody now what could be wrong? Any advice will be much appreciated.

Thanks,

Fernando