Update:
I was wiping my car last Wednesday. I decided to open the hood to clean it. I was shocked to find a receipt that partially covered the hood lock. On the receipt are some battery diagnostics - 12.7 volts, amps and some other technical data. Since, I had my first PMS check up a couple of weeks ago, I believe someone from the service bay left the receipt there and closed the hood with the receipt stuck inside. I'm not sure this has a direct effect on the remote start, but, when I left the car for 3 days without starting it, I remote started it and it worked like a charm. I did this the second time, leaving it for 2 days, it still works.
I think for the remote start to work properly, you really need to check whether all doors, trunk, hood and windows are properly closed without any obstruction whatsoever. I even checked the gas lid whether something was stuck in there, like a dried leaf or something.
Anyway, I'm very relieved because I've finally solved the problem.
I really should have double checked everything before I left the service center. Lesson learned. Whew!!