
Hi Joan,
We first need to take a backup of Outlook data file in Mac. Please refer an article mentioned below.
Export or backup email, contacts, and calendar to an Outlook .pst file - Microsoft Support
We can try Basic Troubleshooting for Microsoft Outlook on Mac
It is a most basic check that you can perform before testing any other method. Go to the Outlook menu and check if the Work Offline option is selected or not.
Click on Tools > Accounts > check the color of exchange account, it should not be orange/amber. If yes, there is a connection problem.
Update outlook for mac, click help > check for updates.
In the Microsoft Autoupdate wizard > select Automatically.
We can also try to generate an App Password for a configured email account and reconfigure an account on Outlook.
Rebuild Office database
Close Outlook for Mac and other Microsoft Office applications.
Locate Microsoft Database Utility. Its default location is Applications/Microsoft Office {version/year}/Office.
Launch the utility and select the identity of the database you want to rebuild. Then click Rebuild.
Rebuild the Office database - Microsoft Support
Reset Outlook on Mac
Quit all Office applications.
Open Finder and go to ~/Library/Group Containers/UBF8T346G9.Office/User Content/Templates, move Normal.dotm to Desktop.
Go to ~/Library/Preferences, locate the files com.microsoft.outlook.plist and com.microsoft.Office.plist, move them to the Desktop (Outlook will rebuild them).
Restart Outlook and Machine
Please update with your findings.
Thanks!