We have made multiple tests with a Surface Pro and Acer Switch 5 (Unity 2018.1.0f1 - Vuforia 7.1.34) and could not make the ground plane work. Always got the messages: 'Could not initialize the tracker' and 'Positional device tracker is not available'. The application runs without any issues on Android.
The Surface Pro appears on the list of supported devices, and we are using recommended versions for Unity and Vuforia. Any inputs?