You have configured and run AD Sync. You notice a user that is present in AD is missing from Central. What is the first step in troubleshooting this issue?

In troubleshooting the issue of a missing user from Central after configuring and running AD Sync, the first step should be to re-run the AD Sync utility. This utility is specifically designed to synchronize users from Active Directory (AD) to Central. If a user exists in AD but is not reflected in Central, there may have been an issue during the initial sync process that prevented the user from being imported.

Re-running the AD Sync can help to determine if the issue was a temporary glitch or a one-time error in data transfer. The sync process will attempt to fetch any updates, including any users that may have been newly created or missed during the previous synchronization attempt. This serves as a practical initial measure in resolving the discrepancy.

Verifying the AD configuration settings or checking user permissions could be relevant steps later if re-running the sync does not resolve the issue. However, addressing the sync itself first is the most direct method to resolve a missing user from the environment. Restarting the Central server generally pertains to service reliability rather than directly addressing issues of user synchronization.