We had a manager changes his domain login from domain\michaelsmith to domain\msmith. We're using MIM sync and I've run a full sync multiple times and when I view the manager's subordinates in User Profile Service, that manager name does not resolve properly. It points to domain\michaelsmith and it's marked with "No exact match was found. Click the item(s) that did not resolve for more options."
This is running on premise in a 2016 SharePoint Environment.