Updating Teams
Step 1: In Teams, select your profile picture, and then click Check for updates. Wait for the banner at the top of the app to indicate that a “refresh” of Teams is needed. The link should be shown about a minute later as this process downloads the new version of Teams. Note: Don't forget to quit Teams and restart!
New Meeting Experience Not Showing? Do this next step!
Are you hoping to be able to see as many of your colleagues lovely faces as possible on your screen in your meetings this week? You can now enable Large Gallery (up to 49 people) or Together Mode (which puts everyone on a shared background together-auditorium style) in Teams when you enable the New Meeting Experience.
Step 2: Make sure to check this box to "Turn on new meeting appearance...". Go to your Teams Profile Picture>Settings>General, then to Application and check the box. (Your Profile Picture is in the top right corner of Teams). Note: Don't forget to quit Teams and restart after checking the box!!
Still having trouble, click below for more details.
New Experience Modes-Large Gallery/Together Mode
Troubleshoot Microsoft Teams installation and update issues
https://docs.microsoft.com/en-us/microsoftteams/troubleshoot-installation
What version of Teams am I on?
To find out what version of Teams you're on, click your profile picture at the top of the app, then click About > Version. This shows you a banner at the top of the app that tells you what version you're running and when it was last updated.