It's a little hard to understand your terminology. However, I'll take a stab at answering your question. My guess is that the black nylon bracket is supposed to engage the track, and it looks like it has slipped down. If you have other door hardware like this, inspect it to confirm that the bracket is supposed to engage the track as I've described.

This could have happened if the silver-headed bolt is at all loose. Get yourself a Phillips head screwdriver and adjust the bracket upwards. You should be able to get the bracket moved up, and then you can retighten the bolt. The problem I see is that the bolt head looks like it has quite a bit of wear on it, possibly as a result of this having happened many times before. If you can't get it tightened down, remove it and take it to a hardware store to get a replacement that you can tighten down.

Let me know if this suggestion has solved your problem, or if you need further help.

Sometimes you have to temporarily remove the floor guide so you can swing the door outward to reengauge the top track. Adjust the height accordingly with a screwdriver.