Microsoft Teams: invalid_resource|AADSTS500014 – Web Applications Stack Exchange

When I am opening the site teams.microsoft.com it showns me the followng window

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  1. Text in the middle states: This indicate that a subscription within the tenant has lapsed, or that the administrator for this tenant has disabled the application, preventing tokens from being issued for it.

What this can mean? What is “this tenant”? What is “tenant” and which of them is “this”?

  1. Button means “Enter”. If I press it, the window reappears.

  2. Text below states: if this doesn’t work, then try to exit and then enter again.

What this can mean? What it “Exit”? How to exit? I have only “Enter” button and not “Exit” one? Exit form where? And enter to where?