After performing maintenance on the vCenter, no data is showing up in Foglight or vFoglight. VMware agent(s) may or may not be in a 'Broken' state.
Maintenance of the vCenter or its hosts while the agent is running causes it to stop running correctly.
Deactivate the VMware Agent, then activate it again:
Dashboard: Administration | Agents | Agent Status
Highlight the agent and press the Deactivate button at the bottom. After it is deactivated, press the 'Activate' button.
If the above does not work:
Restart the Foglight Agent Manager (FglAM). If your environment uses the embedded FglAM, you will need to restart the Foglight service
Deactivate VMware Performance Agents prior to beginning maintenance on the vCenter. Reactivate after maintenance is complete.