I just checked your page and the payment form loads fine for me. I can enter a credit card number and click on the pay button.
You maybe seeing a caching issue. Can you please empty all cache from your site (if you are using a caching plugin), then empty your browser cache and try it?
Which browser you are using to test?
Also, I noticed that you have an “HTTPS” warning on that page (possibly because you are embedding an image using “http” URL instead of “https”. Please correct that.