When go for live it shows forbidden error at checkout page

I installed this plugin and used for sandbox transactions.
It was working fine for sandbox mode.

At time of my website launching I goes for live mode and insert every details and save.
When I go to checkout page, it displays forbidden error.

I need to enable credit/debit card options and paypal payment option.

Kindly help as soon as possible because my launching is delayed due to this issue.

The page I need help with: [log in to see the link]