Active Directory refresh

Good evening.

I have a Fortigate500D configured for LDAP authentication against a couple of AD domain we are running.

Everything works fine when I configure the LDAP Servers, the test button replies "successful".

I cannot see any recent OU and user objects I created, even after a whole day.

Where I could be wrong?

Where can I force/manage the update of the information from AD in the fortigate?

Many thanks for your help.