Solution found!
I was facing same issues. I am from India.
I deleted my plan for using API and created a new plan by adding new card details.
which took me to payment page and ONLY by using AXIS bank credit card, I was able to make the payment and got it working.
You might not have the Axis credit card(if you are not from India) but you could try the process though.
Wish you luck with this one.