Wind Flow lines not visible! PLEASE HELP

Im having a bit of a problem. The wind tunnel worked fine before, but it has started to give some trouble. The wind flow lines are not any more visible in the viewport although the calculation is running. It worked fine before so im sure my system is compatible. Thesis deadline is near please help.

i have tried all these things but still no flow lines visible.

Huzefa, Try clicking Flow Line Settings, in that dialog, click on the wireframe model to select the "wall" which will define which direction the flow lines will emanate from. Also, have you just tried changing the wind direction?