Exchange 2016 - Outlook clients (2010 & 2013) taking a long time to update the GAL.

Hello,

This is a proactive question in case the issue does not fix itself overnight following Exchange maintenance.

We have recently migrated from Exchange 2010 to Exchange 2016.  

The local I.T staff who handle basic management indicate that they created a couple of new Distribution Groups (and removed one); but these are not showing up in Outlook when they click "To:" and select to view the GAL.

As part of the check I've done the following:
1.Checking in Exchange Admin Center | Servers | Databases | Client Settings - Offline address book: (shows the correct Ex2013 OAB).'
2.I switch the Outlook client to run in Online mode - I am able to see the newly created Distribution Groups.
3.I selected to download the OAB.  No errors are reported, but it does seems like it does not complete.

The Distribution Groups were just created today, and I recommended that the clients be allowed overnight to update, but I would like to force the update if possible, and ensure that the configuration is all correct.

Please let me know if there are any steps that I should take.

Regards,

Real-Timer