Thank you both, I re-did that whole track assembling thing yesterday and after a couple hours it works now! I realized that if I don't use the straight tracks, it works. There is something wrong with 2 tracks (one straight and one curve). Not sure if it can be replaced.

@Flare- No, I don't have a voltmeter.

@Bipeflier- I am using my apartment floor (no carpet) to set this.

My learnings from this- 1) each track has to be matched correctly; 2) The orange power cord should be properly connected to the track (it loosens if the track moves slightly);  3) there is some technique involved in placing the engine on track so that it gets power supply; 4) it took me a long time to couple the coaches (needs practice); 5) stay relaxed while assembling and enjoy the process (never work on it after stressful hours at office)

I bought this two weeks ago. I carefully set up the tracks and placed the engine on the tracks. The engine ran after several failed attempts. I lifted the engine and tried placing it again and now it wont run...again it ran after several attempts...this happened a few times. What is the easiest foolproof way to ensure the engine runs on my first attempt of placing it on tracks?

P.S. I have watched all videos, read the manual carefully and I am sure the tracks are assembled perfectly.