If you are troubleshooting Quickbooks scheduled backups not running, you may receive the following error while force running a Quickbooks backup task via the Windows Task Scheduler:

This is typically due to the user who scheduled the jobs not having administrative access to the computer. Sometimes even rescheduling the job as an alternate administrative user doesn't work.

The fix for this is to check the "Run with highest privileges" checkbox in the General tab of the task and re-save it. 

One you've saved the task, try right-clicking and running it again.