General Sliding door issue

[Clintmaximus]

Hi all need help my Fiat ulyesse passenger sliding door has come off its runner how can I get in back in. The metal bar that has the rolls on has come out

 

[bugsymike]

Hi all need help my Fiat ulyesse passenger sliding door has come off its runner how can I get in back in. The metal bar that has the rolls on has come out

Generally on most sliding doors you will need to support the door, unbolt the roller part, reintroduce it in to the runners, then rebolt it to the door, making care to adjust it so it is held firmly in the groove/runners.
You may be able to resort to violence and lever the door back into the runners, it is not advised and you will still need to readjust to take up the slack that caused the problem in the first place or it will come off again.
I have worked on many large sliding doors on commercial vans, they need to be kept well oiled and regularly adjusted as there is a lot of strain/weight on them, try to avoid slamming them and it is best if you use one hand to pull it and the other to guide it closed.
The common thing is they drop with wear and go out of adjustment so the locators do not line up encouraging more slamming which only makes them worse and also breaks the lock mechanism.
Once on the runners and well oiled, I would gently slide the door forward towards it's locating position and check that it all lines up, if not it will require adjustment.