Issue

After adding a secondary email account in Outlook, its folders cannot be expanded. The following error is displayed:

Microsoft Outlook
Cannot expand the folder

All accounts in Outlook are Office 365 / Exchange Online. Creating a new user profile and clearing cached credentials didn’t work.

Resolution

The issue was resolved by running a Quick Repair on MS Office installation.

November 2021
Microsoft 365 Apps for business (16.0.14) 
Windows 10 Pro