When a Schedule is are being viewed in the Analyze directory, the 'Runs' tab lists the available runs for the schedule:
Clicking on the 'View Details' option in the context meu for a failed run will display the 'Run Details' dialog:
Clicking on the link for the data flow will open the run in a read only session. There should be an 'Exit and continue Run' button present in the menu bar at the right hand side:
Clicking the button will attempt to continue to run the scheduled run from the point at which it failed.
Does the user accessing the failed run have the Scheduler role?