If you are using Safari on iOS11 or later, there is a new default feature that prevents tracking of the websites you visit. This is meant to protect your privacy and will be difficult for companies to track your browsing habits. This sometimes prevents access to our payment processor, Worldpay. You will have to turn this off to prevent cross site tracking which will allow you to process your payment.
Depending on the device, you may need to update your settings, which will allow you to proceed.
Safari for Mac:
Open Safari if it is not already open.
Click the "Safari" menu and choose "Preferences" and then "Privacy"
Depending on your version of OS:
Click prevent Cross Site Tracking to disable this setting.
Safari for Mobile or Tablet:
Go to Settings
Click on Safari
Privacy & Security
Turn the toggle 'Prevent Cross Site Tracking' to 'Off'.