zitlic01.desy.de has been retired. Please use - depending on your affiliation - one of the following license server. 

# DESY:               Use !zitlic03.desy.de
# University Hamburg: Use !lizenzsrv9.rrz.uni-hamburg.de AND !mathematica10.rrz.uni-hamburg.de
# MPSD:               Use !flex1.mpsd.mpg.de
# Eur.XFEL:           Use !exfllic01.desy.de



The location of the license file named mathpass depends (of course) on the operating system in use:

Location of the mathpass file:
Linux: /usr/share/Mathematica/Licensing/mathpass
Windows: \ProgramData\Mathematica\Licensing\mathpas
Mac: /Library/Mathematica/Licensing/mathpass


To give some examples:

# Under Linux (example for UNI-HH):
cat <<eof> $HOME/.Mathematica/Licensing/mathpass
!lizenzsrv9.rrz.uni-hamburg.de
!mathematica10.rrz.uni-hamburg.de
!mathematica11.rrz.uni-hamburg.de
!mathematica12.rrz.uni-hamburg.de
eof
## choose /usr/share/Mathematica/Licensing/mathpass    to set the license server system wide
## Please consult https://www.rrz.uni-hamburg.de/services/software/software-thematisch/software-alpha/mathematica.html for uptodate information!

# Under Windows: Set the license server in C:\ProgramData\Mathematica\Licensing\mathpass. The mathpass-file should contain a single line:
!<my-mathematica-license server> 
# in case of DESY:
!zitlic03.desy.de
 
# Under MacOSX: Set the license server in /Library/Mathematica/Licensing/mathpass. The mathpass-file should contain a single line:
!<my-mathematica-license server> 
# in case of MPSD:
!flex1.mpsd.mpg.de
 


To check which license server is being used: