Skype for Business, Address book sync delay
Why have the changes I made to my account not appeared in Skype for Business? Why can't I find a new contact?
Once a change is published to the Exchange Global Address List (GAL), there is still up to a 48 hour delay before Skype for Business clients are all synchronized with the new data. However, if you search for an individual based on their email address (NetID@illinois.edu or NetID@uillinois.edu), you should be able to find the correct entry for someone in Skype for Business.
Also, if your computer's clock is not set to the correct time, it could break your ability to search for contacts in Skype for Business and can effect your Skype for Business client's connection to Exchange.
Sometimes when you search for a contact, you may see a message that says the address book is syncing. This process will complete within 22 hours of the Skype for Business client running and an account being logged in. You can still search for a person by entering their full NetID@illinois.edu or NetID@uillinois.edu (if UA) address while the address book syncs.