1. Check to make sure Outlook software is up to date.
2. Go to the File tab > Options > Advanced > Send and Receive and select the Send and Receive All Folders option.
3. Check if the Outlook contacts are hidden. To do so, go the contacts folder, select View tab > View Settings. Select the Show said items checkbox if it is unchecked.
4. In the same tab, select Reset View to its original settings.
5. Go to the folder list, and make sure the Contacts folder is visible. To do this, select Folder tab> Folder Options> Select the Show these folders item, and make sure it is checked.
6. In the same tab, select Reset View to its original settings.
7. Verify that your contacts are stored in the Outlook contacts folder and not in a PST file. Check Account settings under File > Info > Account Settings to see PST files listed.
8. If the PST file has the contacts, select the File tab > Account Settings > Account Settings > Data Files. Move the PST file selected for contacts to the top.
9. If the Outlook address book service is enabled, disable it and re-enable it. To do this, go to File > Account Settings > Account Settings > Address Book.
10. Lastly, make a backup file of your contacts in case anything goes wrong, go to the File tab > Open & Export > Import/Export. Select the Export to a File option and select Outlook Data File.