Reason: This error occurs when there are some cache files.
TL/DR: Try it on the incognito tab it will work.
While doing your payment that is not processing due to the cache files so kindly follow the steps in the incognito tab so that you will not face this issue.
These can also be one of the reason for your issue:
Reason 1: Incorrect cache files, incognito mode should work - Please try with IE also to be double sure.
Reason 2: Incorrect system time, please check if the system time is correct on your system.
Reason 3: Failed Payment Method - Can you try another payment method for this transaction?
For more detail check this aws tutorial.