several reasons -- but the simplest is usually the case.
1) Task is not defined as General and you are trying to execute a background task.
2) The agent assignment is incorrect -- either via RULES (test via transaction
PFAC) or as above task is not defined as General.
3) Insufficient (SAP) authorisation to execute task / program / access data etc.
4) Sometimes incorrect version of the WF is still active. Ensure the latest version of the WF / Task(s) has / have been activated.
5) There could be an error in the application program. This can happen in Batch and you won´t the see anything on the log.
If you CAN run the WF as Workflow administrator then the program is usually correct so look for reasons 1 - 4.
Using a different Userid can also help as ROLES ( SAP authorisations) defined in the system might not be totally correct for what you are trying to do.
Cheers
Jimbo
