This means that the algorithm cannot find a surface / scene that can be tracked. So you need to move around a bit with your phone until you find a nice trackable scene. You can also refer to this tutorial regarding "How to properly use Instant Tracking".
I get an error message when I want to try instant tracking on Samsung Galaxy S7, the same app work very well on Samsung A7.
"wikitude instant tracking on error with error code 200 and error message no plane was found when trying to start tracking"