Bitcoin checkout with BitPay does not appear to be working

Hi!
Thanks for the wonderful plugin. I have an issue on checkout page. I’m using wordpress 4.5.3 and woocommerce 2.6.4. When I go to checkout and click on “Proceed to Bitray” buttton . It says “Sorry, but Bitcoin checkout with BitPay does not appear to be working.”

Need your assistance, how can I remove this error?

Thanks ??

https://www.ads-software.com/plugins/bitpay-for-woocommerce/