First, try to repair communications: Device Web > Protect > Configure Agent Settings > Repair Agent Communications

If that doesn't work, try these steps:

    1.    Open an elevated command prompt.

    2.    Enter the commands:

        1.    cd "C:\Program Files\Datto\Drivers\util"

        2.    dattosnapshot.exe -ra

    3.    Once done, stop the following agent services:

        1.    Datto Backup Agent Service

        2.    DattoProvider

    4.    Rename the extension of the agent's database file from .sqlite to .old. This will force it to generate a new configuration file. You             can find the .sqlite file at one of the following locations:

        1.    For Windows Vista and up:

                \Windows\system32\config\systemprofile\AppData\Local\Datto\Datto Windows Agent\agent.sqlite

        2.    For installs of Windows XP & Windows Server 2003:

                \WINDOWS\system32\config\systemprofile\Local Settings\Application Data\Datto\Datto Windows Agent

        3.    For older installs of Windows XP & Windows Server 2003:

                \Documents and Settings\NetworkService\Local Settings\Application Data\Datto\Datto Windows Agent\agent.sqlite

    5.    Restart the agent services from services.msc:

        1.    Datto Backup Agent Service

        2.    DattoProvider

    Once done, try a repair again via Device Web > Protect > Configure Agent Settings > Repair Agent Communications.