@hermann-san
Interesting. Did it just simply not start or did you get any error messages?
Why I wonder:
The example file gives the correct working directory (line 11). And if one does try it manually via shell, it seems to work:
cryptpad@server:~$ cd /home/cryptpad/cryptpad
cryptpad@server:~/cryptpad$ /usr/bin/node /home/s_crypt/cryptpad/server.js
Upon this the server starts, so no output, but I can load the cryptpad web page without problems.
I have not tried it by defining the service and actually starting the service. So sorry, if I'm wrong, but I'm interestend and curious.