Redmi 3s prime & Flipkart gv- help needed urgent.

I want to purchase redmi 3sprime from flipkart and for that I am trying to utilise pockets 10% cashback offer- by buying fk gv and then using them to purchase redmi 3s prime. Now my concern is-

1. I am not able to buy fk gv from flipkart website. Every time I proceed to payment it just gives me error. Am I the only one facing this or is this some general issue.

2. Is there any other better ways to purchase redmi 3s prime with a discounted price.

TIA.