I have Active Directory setup as my primary user directory in JIRA. Works fine most of the time. I have over 400 users and anytime a new user comes in I grant them permission by adding them to the AD group AllJIRAUsers. Out of 400+ users, all but 2 sync and show up in JIRA User Management. I haven't been able to figure out why those specific 2 users will never sync and show up in JIRA.