Why I am getting an error "no payment method for the order amount" at the checkout page?

Whenever your site uses a payment  method that requires the user to enter the credit card details on your site (not sent to another providers website for payment, such as PayPal standard), the site needs to be secure. The thing that is responsible for this error is the lack of a SSL certificate. You need to have our support team purchase and install either a single or wild card SSL certificate (depending on the number of domains and sub-domains needed). Once the SSL certificate is installed you need to change the site from a non-secured site to a secured site from Admin > Site > Site Name > Settings > Domains tab > Select the site name and hit “Set as HTTPS”. This will make your site a secured site and you will stop receiving the error message. 
As of 2017, secure certificates can be enabled on any Pressero site and installed automatically for any site. Any old certificate ordering information no longer applies. Please check announcement and instructions on articles below:
Change to the Automatic Certificate System (HTTPS/SSL/TLS) for Pressero
What do I do when I'm ready to "go live" with my Pressero site?