Synology DS1513+ - Install of upgrade fails

Hi
I wanted to use Plex now on my Synology Server but I have a problem.
The basic install is ok and than he ask me to manualy update and this always fails.
I even tried to uninstall it and than install the package manualy from scrap but this didn't work too.
Any ideas where I can see and find the problem? Is the new version incompatible with other packages?
Thanks in advance