Sophos Mobile Security web filtering with Google Family Link cannot be enabled on a child's device

On two devices, a Galaxy S4 running Lineage OS 14.1 and Galaxy S5 running standard android 6.01, when you install Sophos Mobile security alongside Google's Family Link for children's devices, you are unable to enable the web filtering. 

When clicking the enable slider, it immediately returns to the off position, it doesn't prompt to enable the sophos accessibility service, nor does it bring you to the accessibility settings.

If you manually enable the sophos accessibility service, you are still unable to turn on the filtering service.

 

Has anyone else had this experience, and/or been able to turn on the filtering?

 

With thanks,
Liam