calibre-server not starting

I am running calibre-server from /etc/init/calibre-server.conf so it should start when the server starts. It was working but now it doesn't. I get no error message.
I can run exec /usr/bin/calibre-server --with-library "/home/cts/calibre-library" from a command prompt and it works. Any ideas what to check for? I am pretty new to Linux and running the latest version of Ubuntu. It was working fine for a while but now it is broken.

Thanks,
Paul