XPe has a special writes protecting filter enabled, at least on these Samsung LCD-s.
It means, that for user, it seems like he/she successfully installed something, but after machine restart original state is back. That is one of the strong arguments of XPe, that it does not get corrupt over time or infested by viruses.
This write filter has to be disabled through command line before installing something and after that enabling again.
But this means also, that Signage Player, on every reboot, will start loading info from server all over again, because previous state is flushed.