Hi @Liz_Ziser, thanks for reaching out! Our support team can help you recover the user previous instance, you can contact them following the steps in this thread: How to contact our Support Team ✉.
Once the user is a member again, your Admin can remove them from the Admin Console and a Private Project will be created for the Admin containing both complete and incomplete tasks previously assigned to the former employee. Then you can reassign these incomplete tasks to another user or organizing them better so it doesn’t affect your metrics.
I hope this helps!