The CCDC local licence server stores a lock file in /tmp and some operating systems such as CentOS and RedHat may have standard /tmp cleaning policies that will remove this lock file after a set period of time, typically 10-14 days.
This page contains details on temp files and how they are cleaned up by default with RedHat:
The licence server we use will create a lock file in /tmp of the form lexlock-* - it's this we need to ensure is not removed.
So based on the article linked to above, the answer is to
cp /usr/lib/tmpfiles.d/tmp.conf /etc/tmpfiles.d/tmp.conf
and append the following lines:
# Do not delete LexFloatServer files
Note that it's mandatory to copy the tmp.conf file using the same filename.
Other approaches would be to touch the lock file regularly, so it is never old enough to be cleaned up. Or the licence server could be restarted regularly so the lock is never old enough to be removed.