I have a backup task that is set to daily back up. I check the "manage task" and the status is "waiting" and has not backed up for 3 days.

Can you explain what "waiting" is and how can I avoid it?

By the way.. I tried to stop the task and start it again, and it is still "waiting:"

Could you please quit the application by right clicking on the backup icon on bottom-right corner of your screen and select Exit? You can then restart the application. Let us know if it fixes your problem. Rebooting your PC may also fix the problem.