After changing your license to one that includes data control (where your previous license did not include the feature) all computers report to the console that a reboot is required.
First seen in
Sophos Anti-Virus for Windows 2000+ 10.0.4
To ensure your computers are fully protected by data control the reboot alert is generated.
Though no driver has been deployed to the endpoint computers (the more common reason that a reboot is required) we cannot guarantee data control is fully implemented until a restart on the endpoint has been completed.
What To Do
To ensure full protection the computers must be restarted.