My PayFast Plugin returns an error

I bought and installed the PayFast payment plugin yesterday. I have already configured my Merchant ID, Merchant Key and the PDT Key. However, when I tested with a live transaction, I got the:

The supplied variables are not according to specification:
signature : Generated signature does not match submitted signature

Message.

I have attached the photo for your reference.

As replied via support ticket, look like the problem causes by something wrong with the Payfast account you are using. If anyone gets this same issue, please try to test it using sandbox account provided by Payfast www.payfast.co.za/documentation/testing/

If it works well with sandbox account, that mean there is a problem with your account and you will need to contact Payfast support and ask them to check it for you

Regards,

Tuan