I don't think I've ever had to sign into Teams (PR Outlook, for that matter) in my desktop. Mobile, I have to after changing my password. I assumed all the MS apps signed me in with my domain login on my laptop. On weird issue I have is things like SharePoint and Dynamics 365 asking me to sign in again after its already brought up the site, and clicking the button to do it just brings a blank pop-up that immediately disappears and I'm logged "for real" I guess.