Upon selecting the blurr mask and by pressing the tracking button (and subsequent application of effect) the blue mask outline with handles disapppears and I cannot get it back. In the YouTube video the mask stays on.
The effect of mask plus blurring is applied to the video, but possibility of re-tracking is lost.
Sometimes the blue mask disappears if your object goes out of frame and similarly the mask also goes out of frame. You can move the CTI to the start of the clip and then move the CTI slowly to see the mask movement.
Also, would be better if you can share a screen recording of the issue to help us better understand it.