It's something that I have experienced myself. I used to be a regular person on paytm and used it a lot but not for online shopping but for recharges and online payments.
I even used paytm wallet. It is an easy way and was excellent. I used to use it through my Facebook account and had some balance left in my wallet. And after the update now the application is not connecting with Facebook and I can not again use my account now.
The balance left in my account is just like a loss to me. No ways to recover it now.