Hi Mystique,
I'm having the exact same issue (using paymate express v2.3 contrib), when a customer gets redirected to paymate for processing, all is good, details get filled in *accept for 'ref' (another story) , if you wack in a dodogy credit card number, paymate 'will decline' the transaction then redirect the customer back to the cart, displaying 'Your payment was approved! Thank you!' ....
Lol Im sure this is not what we want to happen! I think the issue is paymate is no longer parsing the correct 'response code' back to the cart perhaps its just defaulting to 'PP'? The cart then has no idea that the payment is declined. Sends out an processing order email to the customer and you, while the transaction has be declined!
The only way to varify that the transaction has been accepted is to manually log into Paymate and check your payment status.
I guess the paymate contrib still needs a lot of work to get it fully dynamic like the paypal contribs....
I'm trying to dig into the code, but Im no php guru...
Drop me an email j.chen(at)ishoppe.com.au if you like. i don't frequent the forums much...
Good luck
Response Code Definition
PA Payment is approved
PD Payment is declined
PP Payment is processing