Outlook 2021 does not update new mail

I finally migrated from our old Zimbra 8.8.15 to a new shiny Carbonio CE server. The Carbonio server works fine but my issue is with Outlook and I'm curious if anyone else had this problem and got it sorted?

The issue is that after the move to Carbonio, Outlook does not update the inbox like it used to before the move. I have to select a different folder and then go back to the inbox to see any new email. Same on my coworkers Outlooks. Any advice would be greatly appreaciated!