[Koha] Schedule::At

Hello all, We have faced this new problem in koha 3.02.05 when trying to open the link http://mu.maktabat-online.net:8080/cgi-bin/koha/tools/scheduler.pl which concerns with the Task Scheduler<http://mu.maktabat-online.net:8080/cgi-bin/koha/tools/scheduler.pl>we get this error Software error: Schedule::At: Can't exec getJobs command: No such file or directory also after upgrading to koha 3.02.09 we faced the same problem the log file also contains the same error message also we removed the Schedule::At module and reinstalled it we get the same error again any idea plz to fix this error??? thanks so much