Transition - "cannot assign issue to nonexistent user

[hristo.iliev]

Hi , I am unable to move an open issue through my workflow. I keep getting an error of "cannot assign issue to nonexistent user". It seems that you have tried to perform an illegal workflow operation. If you think this message is wrong, please contact your Jira administrator."

[Kian Stack Mumo Systems]

@hristo.iliev, 

It seems that you have a post function on your workflow which was assigning the issues to a user that no longer exists.

Take note of the issue type/types where this is occurring, along with the transition where this is occurring. Navigate to Project settings > Workflows and edit the workflow tied to the issue type which was throwing the error.

Look for the specific transition which is failing, and click on it. A little box should pop up that looks like this:

Click on the Post Functions link and check to see if one of them looks like this

This user will likely be one that doesn't exist any more. Just remove this post function and save your workflow.

[hristo.iliev]

@Kian Stack Mumo Systems  thanks a lot for your help, i fixed it with changing of "assignee will be cleared" to "assignee will be set to default"

[Prateek Yadav]

@hristo.iliev , for me the message shows name of a particular user who is no more with the organisation. That user is no where specifically mentioned in the post function or any transition. Can you help me in understanding why that should happen that his name is coming in the error message? It must be picking it from somewhere.

[Paulo]

Same case here, we have a deleted user but I don't know where that user is being picked up from

[William Crossland]

same issue here. not sure where the user is being assigned. no clues in the logs