SAP Alert Not Triggering

Hi,

I seem to have an issue with two SAP Alerts that I setup.

1) One Alert is set to trigger every day morning at 9 AM.

2) One Alert is to trigger every day night at 11 PM.

The first alert set to trigger in the morning is works fine Monday to Friday. But is not triggered on Saturday and Sunday.

The second alert set to trigger at 11 PM at night is never triggered.

Can anyone tell me why this happens? Could it be because no SAP User is logged into SAP at these times? Or could it because of some other reason.

Thanks,

Krishnan