Most probably, this error happened because of the wrong ValU activation, or you have used a test ValU number in LIVE payment (vase versa).
In this article, you will be going to know about:
How to investigate the reason that caused this error?
You can investigate the reason for such an error from the "API debug log" by navigating to the Developer’s menu > Testing > API Debug Logs (within your desired profile).
Or you may get the error directly from the payment page once you click on the "Show Instalment Plan"
Reason #1: Using test ValU number in a LIVE profile or vice versa
This means that the customer has used a test ValU number in a payment with a Live profile or the vase versa.
To test a live payment, merchant can enter a LIVE ValU number to make a purchase and then refund it.
Reason #2: Wrong activation of ValU activation
If you are sure that the issue is not from the previous reason, kindly send an email to "[email protected]" mentioning that you have an issue with ValU activation with the error "Invalid HMAC".