Outlook 365 Desktop Application will not expand secondary email

Hello,

I have a user who has multiple email addresses for our various companies. One address, intermitted, will not expand the mailbox in the desktop application. Our workaround is to remove that address and reapply it to the application. This allows it to work for a short time, then it will not expand anymore and we have to remove it and add it back once again. Anyone see this issue and have a permanent fix?