This article describes the cause and possible solutions for the error: Backup failed because this encrypted agent's master key is unavailable.
This can happen when the Datto device is rebooted. Upon reboot, you need to enter the passphrase for any encrypted agents to allow for backups to continue:
1. Log on to the device through the Remote Web
2. Navigate to the Protect page
3. Select the Decrypt now box, and enter the required passphrase.
This can also be done through the main home page if you click the lock icon next to the server's name
4. This will decrypt all agents with the same passphrase. If there are multiple passphrases in use, please decryptt each agent individually that has a different passphrase