Account Engagement error 'This user can not be deleted as they are selected as the point of contact for one or more notification categories'

Check to see if that user is set as a point of contact for any of the categories under Product and Service Notifications in your account settings.

In Account Engagement (Classic) https://pi.pardot.com/account, or click the Settings wheel at the top right and select Settings.

In the Account Engagement Lightning app, select Account Engagement Settings.

If the desired user to be deleted is listed as the point of contact for any of those categories, you must edit and change the contact before deleting the user. Please refer to Edit Product and Service Notifications to make those changes.