I got the problem when I made Ground Plane Emulator on PC with Webcam, in my case I got both file VuforiaEmulator.xml and VuforiaEmulator.dat. The problem is when in Unity Playmode I got the Error: Could not load emulator database.
I already enabled Vuforia Augmented Reality.
I use Vuforia 8.0.10 with Unity 2018.2.5f1 run on PC.
Please check image attached below.