Sometimes when you try to delete a marketing user, the option is unavailable. This happens when the user has Admin privileges. Administrators can't be deleted, so you should first remove the Admin permission to remove the user.
Here's how:
- Go to Settings > Users.
- On the Marketing Users tab, hover over a user and click Edit permissions:
- Toggle off Has administrator access. & click Save Changes.
Now, you will be able to delete this user.