Why can't I assign work items to a team member?

Question

In my organisation, I have tried setting up my team member as having Basic Access and Stakeholder access. However neither allow me to assign a work item to her.

She uses an gmail address to log in.

In my organisation->Users->User I make her a project administrator but it reverts to Custom.

In my project->Teams-> MyTeam I can see we are both members

However when I go to assign a work item there is only 1 person in the combo box.

How do I enable the ability to assign work items to her?

[Update]

I think a Microsoft Account or AD login is needed looking at this quick start

However if gmail accounts don't work then we should be prevented from adding them as users.

Answer 1

because I did not realize that I need to type part of the users name and click search. I was mislead by the combo box with just my name in it.

Answer 2

When you invite a user, you are only inviting an email address and that could be Gmail, Apple, or Amazon. When they select the invitation link, they are taken to the experience where they are asked to sign in with their Microsoft account (MSA).