Microsoft sent us the below steps to follow. Have not tried them as our effected user if out of office for 2 weeks.
• Press Win + R and type below commands one at a time in the blank box in affected user's machine and hit enter:
outlook.exe /resetfolders
outlook.exe /cleanviews
outlook.exe /resetnavpane
outlook.exe /resetfoldernames
• Create a new Outlook Profile from Control Panel for affected user and check the behavior.
• Move all the OST's to a different Folder from the below location:
C: Drive> Users> Click on the users Profile> Appdata > Local> Microsoft Outlook.
• Update Outlook application to latest version and check the behavior.
• Run the below PowerShell command:
Revoke-AzureADUserAllRefreshToken -ObjectId "ObjectID of the affected user"
Reference article: Revoke-AzureADUserAllRefreshToken (AzureAD) | Microsoft Learn
• Clear credentials from Control Panel> Credentials Manager> Windows Credentials (Remove all Office related credentials).
• Run a Quick and Online Repair.
run a quick repair (Start > Control Panel > Programs and Features > Office 365 > Change > Quick Repair
run a Online repair (Start > Control Panel > Programs and Features > Office 365 > Change > Online Repair
• Disable Hardware Graphics Acceleration.
• Compact Outlook OST Files by following the below steps:
Click File tab, go to Account Settings > Account Settings.
Click Data Files, select your accounts, and click Settings Now, click Compact Now and hit OK
• Change the Outlook Channel:
cd C:\Program Files\Common Files\Microsoft Shared\ClickToRun
OfficeC2RClient.exe /changesetting Channel=SemiAnnualChannel
OfficeC2RClient.exe /update user