Nobody knows. Simply play with the options. Chances are, though, that it's simply not possible. The footage could simple move too fast or have something implausible about it - it is artificial, after all.
The problem could be the codec you used to compress your screen capture. The problem could be that there is so much movement in foreground objects compared to the background objects that the software just can't figure out what it should be tracking. Motion tracking software is limited in what it can do automatically. Even the best, Bojou, requires a lot of handwork on certain shots.
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