Paytm is down and possibly has been for quite some time. Wanted to purchase something but just could not access my account( Thursday 24th Dec 2015, 1630 (GMT +05:30). I was suprised but saw the same bug on my smartphone too.
A prolonged down period could mean its because of either an external hacker action or an undiscovered internal bug. However seeing a site down for ages makes me really wonder about the IT team. They have recently expanded and it could be growing pains.