Schedule to system suspend failed


after installing and running rockstor with one HDD in a pool everything works fine.
I’v created a scheduled Task to put the System in suspend with enabling System RTC wake up which works fine.
Then I decided to uncheck RTC wake up. Now the “last run” says “failed”.
Where can I find the reason (log) for this failure?

Thanks in advance
Edit: rtcwake works only with wake up time. So perhaps this is the problem. You have to enable RTC wake up time (?)