Add user to a call

[Phoxy]

When two people in my organization are in a Teams video call or voice call with each other and they select the "people" button they can type the name of the third person. The full name of the third person even appears in the select box, but they are not able to click on the name and there doesn't appear a box "invite" to add the third person to the current call.

I have already searched in the admin dashboard for a policy setting that would prevent it but I can't find it. Any help is welcome?

[#2]

@Phoxy There isn't specific button, you should just click on the persons name when it appears in the list and they will then show in the participant list while it's calling them.

Try in a browser if it's not working in the client, if that works reinstall the client.

[#3]

Thanks for your response.
That is the whole problem, we aren't able to click it. It appears to be not clickable. As if clicking has been disabled.

[#4]

As you suggested I tried to add a user through the browser to a call but it didn't work either. But when I try to do it through the browser I get an exception "Unexpected exception", but I can't find what the details of the exception are.

The problem is that our whole company isn't able to add someone to a call (while we are in a call). That's why I think it is a policy setting but I have no clue what setting it should be?