Upgrade button is greyed out when attempting to upgrade FglAM host in the agent hosts dashboard (4249135)

Foglight Agent Manager (FglAM) adapter in the Agent Adapters dashboard is clearly on a higher version than the existing FglAM hosts. However, the "Upgrade" button in the Agent Hosts dashboard is greyed out when the outdated FglAM hosts are selected. As a result, FglAM host upgrade cannot proceed.

CAUSE #1

FglAM installers for the specific OS platform has not been deployed on the Foglight Management Server (FMS).

CAUSE #2

The FglAM adapter requires a restart

RESOLUTION #1

1. Deploy the full FglAM cartridge installer to the FMS and enable it via the "Administration | Cartridges | Cartridge Inventory" dashboard.
2. Upgrade the FglAM host.

RESOLUTION #2

1. Navigate to "Administration | Agents | Agent Adapters"
2. Deactivate the FglAM-Adapter
3. Activate the FglAM-Adapter