'No Administrator found' workflow error

Help! Why am I getting the error 'No Administrator found'?

This is another symptom of the org buffers being out of sync. Basically you have made an organizational change that is incompatible with the previous state. When executing the work item it gets confused with the old (buffered) and new org data. As above, SWU_OBUF should reset all buffers.

Workflow : Other Useful Links :
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Raising ABAP OO events for workflow