I am unable to move an open issue through my workflow. I keep getting an error of "cannot assign issue to nonexistent user (username redacted). It seems that you have tried to perform an illegal workflow operation. If you think this message is wrong, please contact your Jira administrator."
I am using Jira Core v7.5.1 (I know it's end of life) We have had multiple contract companies do work on our instance of Jira, however none of them have left any continuity. Any help would be appreciated.
-John