Hi,
The error probably indicates that you have an old version of a payment plugin you installed in the past and which isn't included with HikaShop.
Since your server doesn't show the error message for some reason, I can't directly point out which one it is.
However, there is a way to find out.
Go in your plugins/hikashoppayment/ folder via FTP and rename the folders in there one by one to something else in order to deactivate the payment plugins and each time you change one, refresh the page with the error. At some point, the page will display and you'll know that the last one you changed is the problematic one.