Why IP phone doesn't synchronize contacts from S-series PBX?

Please follow this guide to check your configurations first. 

https://help.yeastar.com/en/s-series/topic/configure-company-contacts-permissions-for-users.html#manage-company-contacts-permissions-for-contacts__view-company-contacts

Since the IP phone default can only automatically synchronize the PBX contacts every 6 hours.

If you need to get the contacts right now, here are 4 solutions to make the IP phone to get the contacts from S-series PBX immediately. 

1. FIRST CHOICE. On IP phone screen, go to Remote Phonebook page, click 'Update'

2. Go to IP phone web->Directory->Remote Phone Book, to click 'Confirm'

3. Reboot the IP phone

4. Go to IP phone web->Directory->Remote Phone Book, set the 'update time interval' to 3600 seconds (Yealink allows the minimum time is 3600). With this changes, the IP phone will synchronize the contacts from S-series PBX every 1 hour.