Yes, this is going to be a server related problem. The issue is most likely caused by the phpQuery library. LayerSlider needs PHP 5.3 or newer and the Multibyte String Extension (mbregex aswell which is a part of it) to be installed on the server. The hosting provider can assist your customer with this and help installing or updating them if needed.
Hey RadiusTheme,
Yes, this is going to be a server related problem. The issue is most likely caused by the phpQuery library. LayerSlider needs PHP 5.3 or newer and the Multibyte String Extension (mbregex aswell which is a part of it) to be installed on the server. The hosting provider can assist your customer with this and help installing or updating them if needed.