Checkout not working (Please help asap)

Hello I am attempting to checkout with a 100% off coupon and using money and the checkout screen is not working and returning back errors. - Error - Properly installed header code, it is not installed twice. I triple checked.

Has anyone ever ran into this or encountered this issue.

You can test this yourselves on your site to see if you experience any issues.
Site: viraltok . co / pricing
100% OFF coupon code: TEST100

Please help me as soon as you can, need to launch this protect asap.