User 'EKYRIA/UC' cannot be deleted because of active tasks.
From the message, it sound like there are still task out on the system that is still running/not.
Try these step:
Go to client on which you wish to remove the user > open Process Monitoring Perspective > Filter > Time Frame: select the suitable time range & User Object: select the user that you want to remove > Click Filter button (leaving option Include deactivated tasks unchecked) > then you should see the tasks that are still active under that particular user Cleaning the tasks that are not deactivated then remove the user.
No active tasks resided on Process Monitoring Perspective for this particular user.
Nevertheless the user could be deleted now.