How do you troubleshoot an offline Bamboo agent?

An agent showing offline in the Bamboo admin console is a connectivity or process problem, and the checks go roughly in this order:

1. Confirm the agent process/service is actually running on the host; restart it if it has crashed.
2. Check network connectivity from the agent to the Bamboo server's configured URL/port — firewalls and VPN changes are common culprits.
3. Check the agent's local log file for authentication or version-mismatch errors (agent and server Java/Bamboo versions should be compatible).
4. Verify disk space on the agent host; a full disk can silently prevent the agent process from writing its working directory.
5. Confirm the agent hasn't been disabled or left "unapproved" in the server's agent list — new or reconnected agents sometimes need manual re-approval.

If the agent reconnects but jobs still don't get scheduled to it, the next check is whether its capabilities still match what jobs require — a capability that silently disappeared (e.g. a JDK path that moved) will leave the agent online but never selected.