Hello Barbara,
This usually happens because of authentication issues, profile corruption, or the toggle between “New Outlook” and “Classic Outlook” resetting after an update. Here’s what you can try in one go, Check if the New Outlook toggle is still turned on in the upper-right corner of Outlook. If it’s off, switch it back on. Next, verify your account under Settings → Accounts → Email & accounts to make sure your correct account is signed in.
If that looks fine, clear the Outlook cache by closing the app and deleting files from C:\Users<YourUsername>\AppData\Local\Microsoft\Outlook (your emails are safe on the server). If the issue persists, run a Repair on Outlook via Control Panel → Programs → Apps & Features, then sign out and sign back in through File → Account Settings → Manage Profiles.