Because the agent was added without the encryption at the beginning it would be necessary to delete it and re-added it again with the encryption password. Follow these detail instructions to do this:

1. Remove the Agent
1. From the Datto web portal, click on the Protect tab, then select from the list the agent that you want to remove.
2. On the left side, click on the link Remove Agent.
3. Confirm that you want to delete all the backups store for this backup by entering the phrase requested.
2. Re-Add the Agent
1. Back to the Protect tab, click on the button Add New Agent on the upper right side.
2. Choose Agent Based System. 
3. Enter the IP address of the server that was removed.
4. For the option, Do you want to create this agent based on a template or another agent?, choose Yes, please. Then Select a Template or agent from the dropdown. You can choose any of the servers you have already added to copy the settings it has, like scheduling, retention, screenshot verification schedule, etc. 
5. For the option, Do you want to encrypt your backups?, select Yes, please. Then enter a Passphrase. This password should be the same you have been using to add the other servers to the Datto, so it won’t be confusing to remember it. You have to save this password securely because we cannot recover it, and if you lose it we would have to delete the data and re-pair the agent again. 
6. Wait until the pairing process completes.
7. After that, you'll be redirected to the Protect tab and from there you can Start a Backup.
3. Start a Manual Backup
1. From the Protect tab on the portal, locate the agent in the list, then click on Start a Backup.