Ola Cabs / Ani Technologies — issue while applying coupon code

I installed ola application using a referral code. I received rs. 50 referral code after that. Now, while booking my first ride, when i select the code, it gets successfully applied but disappears automatically in few seconds. Same issue is happening with my wife's login. There are no terms and conditions mentioned in this program in ola application. I tried for all available options (Mini, micro etc) with different payment options. But it's not working.