Timer Job Service – Non Applicable

Hi,

I’m a beginner on SharePoint Foundation 2013 and i’ve done a SharePoint farm. I don’t understand why but some jobs enumerated in my tasks job, has in last execution time “Non Applicable”. The task are default sharepoint tasks

Also immediate alert are “Non Applicable” so they don’t work !
I’ve passed 7 days looking for it but i didn’t find the problem.

I’m totaly lost 🙁 If someone has an idea it will be helpful for me 🙂

Thanks,