Hi,
Make sure that the "debug" setting of the payment method is activated in the System>Payment methods menu. Then, try again. While you do, look at your browser's console. It might output error messages with important information on the problem.
Also, after you get the issue again, go to the HikaShop configuration page and look at the "payment log file". It should contain information about the issue too.
Please provide information from the console and from the log file and we should be able to tell you what to do.
When replying, you can use the "Reply Topic" button, instead of the "Quick reply" button. That way you can use the confidential tags around the log / error data so that only our support team will be able to see it.