Fleetsmith will only escrow FileVault 2 Recovery Keys for devices Fleetsmith encrypts.
Devices encrypted prior to Fleetsmith—or devices with FileVault 2 manually turned on via "System Preferences"—will have a "Managed" Encryption status on a device's page.
To allow Fleetsmith to escrow a FileVault 2 Recovery Key, please manually turn off FileVault 2 on the device. Then, allow Fleetsmith to be the source to re-encrypt the device by enforcing FileVault 2 on the profile the device belongs to. Once Fleetsmith re-encrypts the device, the "Managed" status will change to "Show Key".