The Contacts application has the ability to configure contacts from an Exchange mailbox. Updates to Mac OS X in the Summer or Fall of 2020 have introduced issues preventing the sync from functioning successfully for certain users. Apple support has advised us multiple users encounter this same issue, but they do not have any ETA to the resolution of the sync issues experienced within the Contacts application.
A temporary workaround is to enable mail to all contacts to be viewed within the Contacts app. Wait until the contacts sync and then disable the Mail sync again. Please be aware that this will download email within the Mail application on your Mac. We do not recommend leaving Mail enabled if you are using Outlook, since reminders will not dismiss.
1. Open Spotlight by pressing command key (⌘) and space bar or select the magnifying glass at the top right and search for Contacts
2. Select Contacts and then Accounts on the menu bar.
3. Find your Exchange Account and select the checkbox next to Mail
4. Select Contacts on your dock and you should now see contacts syncing.
5. Open System Preferences and unselect the checkbox next to Mail