I have checked your issue on your site when I add a product to the cart. Then I check the checkout page and all is working fine. The payment option of credit card and also the checkbox (I have read and agree to the website terms and conditions).
I have made a video for you to check that it is working fine for me here is the video URL: https://streamable.com/6obkdm Please watch the complete video for a better reference.
Regards 8Themes Team.
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.