The license key is stored in the ./config/sos.ini file.

 [licence]
 ;                         licence key for non-commercial use of job scheduler starts with (SOS-DEMO-*)
 key1                    = SOS-DEMO-1-L54-4-7-22-???????
 
 ...

The JobScheduler must find the sos.ini file. For this it has the start option -sos.ini=[path to sos.ini file]

Normally this option is set via the installer in the ./bin/jobscheduler_environment_variables.sh

 ...
 SCHEDULER_DATA="/home/[jobSchedulerUser]/sos-berlin.com/jobscheduler/[jobSchedulerId]"
 ... 
 SOS_INI="$SCHEDULER_DATA/config/sos.ini"
 ...

or in the ./bin/jobscheduler_environment_variables.cmd respectively

 ...
 set APPDATA_PATH=C:\ProgramData\sos-berlin.com\jobscheduler\[jobSchedulerId]
 ...
 set SCHEDULER_DATA=%APPDATA_PATH:\=/%
 ...
 set SOS_INI=%SCHEDULER_DATA%/config/sos.ini
 ...

If you get the error message

No license key was found or License key has been expired.

then check the sos.ini and the jobscheduler_environment_variables.(sh|cmd).