Azure Devops Inviting Users doesn't work

Question

I have invited a user to my Azure Devops org and project.

I invited them in https://dev.azure.com/org/_settings/users using Add Users

Added them Project Collection Administrators in https://dev.azure.com/org/_settings/groups

Set them as an administrator in https://dev.azure.com/org/project/_settings/

Set them as project administrators in https://dev.azure.com/org/project/_settings/permissions

And yet when trying to access the project, they get:

What am I doing wrong? What am I missing?

Thanks