Could not connect to slideshowpro.net (using cURL): Couldn’t resolve host ‘slideshowpro.net’.

After a bit of digging on their forums it seems the new Plesk firewall is blocking some unwanted traffic. e.g. curl calls to the slideshowpro.net server. To get round this, you need to add a custom rule which enables Director to talk to their server. Easy when you know how!