The most common reason for ‘Merchant not participaing’ is when testing your acquirer agreement through Quickpay Manager. In most cases the error is because of problems with Mastercard and 3-D Secure.
In general you get the error because one of the following:
It is due to the Mastercard agreement not being active in the 3-D register, as it has to be manually enrolled. Typically it takes 48 hours for the enrollment to be active. If the error persists beyond this point, you will need to contact your acquirer, and have them re-enroll the agreement.
The ‘Terminal operator business number’ and ‘International business number’ are always two different credentials. If an international business number has not been included in the information you received from Nets, you should contact Nets to retreive this.