Exchange global address list not updating
If the expected changes aren't present in the GAL, the changes will not replicate to the Offline Address Book.
NOTE: If you change your on-premises Active Directory schema, but the Microsoft Azure Active Directory Sync Tool still doesn't synchronize these changes correctly, go to this Microsoft website to continue troubleshooting this issue: Troubleshoot directory synchronization Manually download the Offline Address Book in Outlook.
Corruption may have occurred if Outlook stopped responding.
For more information about how to create and to set up an email profile in Outlook, refer to the following article: Create a New Outlook Profile NOTE: If the Offline Address Book issue wasn't resolved by using steps 1 through 5, follow this step for validation before you call Microsoft Support.
For me, new colleagues are not showing up and the contact pictures aren’t displaying either.
They do for my colleague sitting next to me, so I don’t think it is a server misconfiguration or something like that.
If the update mechanism appears to be broken for you, it could be because of a corruption in your OAB or in your mail profile.
If the issue is resolved, it's unnecessary to continue to the next step.
If the issue isn't resolved, proceed to the next step. To do this, ensure that you can view any changes in the GAL by using Microsoft Outlook Web App.
This solution is available through Microsoft or through a third-party provider.
Microsoft does not specifically recommend any third-party provider or third-party solution that this article might describe.