Problem with login to Microsoft Teams

[Przemek1065]

We use the Teams work and school application in our company. Thirty users log in and use this application without any problems, while one user has trouble logging in correctly. The following messages appear:

"You're missing a lot! Ask your administrator to turn on Microsoft Teams in your organization ..."

or

"The selected user does not exist in the tenant ... and cannot access the application ... in that tenant. First, you need to add an external user account in your tenant. Use a different account."

What could be the cause in this situation?

[#2]

Hello
That is usually caused by licensing, what is the Teams license assigned to the user?

[#3]

@Andres Gorzelany 

There should be a free license (work and school). Other users have such a license.

How can this be checked? Possibly a change so that the user can use the app normally?

[#4]

Do you have access to the admin portal of the tenant?

https://learn.microsoft.com/en-us/microsoftteams/user-access

[#5]

Ok, but we don't have Microsoft 365 or Microsoft Azure. Do we have an admin portal then?

[#6]

Ok I understand now the version you are using, was this person invited to use Teams right? did this person accepted? is using the same email to log in?

[#7]

Yes, this person invited to use Teams and accepted them. Uses the same email to log in.
We use work and school version, but it may have had a different version previously installed by default.
We checked on other devices and the same problem.

[#8]

Does anyone have idea how to solve this problem?

[#9]

Did this work in the past for the user and stopped working or it did never work?

Did you try inviting this person again?

[#10]

It never worked..
We added a new person to organization. We sent invitations. Nothing solved the problem.