If your Teams client appears to be out of date, you can verify this by checking the current version. You can then manually check for updates if it is.
Checking current version
Click on the … button in the top right corner of Teams, then About > Version.
A small banner will appear that shows the version of your Teams client.
Microsoft currently does not have a way to check the version number of the most recent release of Teams. Comparing to peers versions is often the quickest way to see if you’re up-to-date. (There may be slight variation in version numbers, but if they are very close that may be fine.)
Checking for updates
If your version does not seem to be up-to-date, you can manually check for updates. Click the portrait in the top right corner of Teams, then Check for updates.
A small banner will appear that indicates Teams is checking for updates.
If an update is installed, the banner will ask you to restart Teams when it completes.