If you get an error message similar to the one shown below, then it is possible that you are using a Windcave developer/test account that that this account has been setup on the incorrect Environment.
On the Merchant Facility, there is an Environment picklist field. This is normally set to Sandbox for developer/test accounts. You can try changing this to Production.
If you get an error when trying to save, then it is likely the validation rule "Merchant Facility Validation Rule (Managed)" needs to be de-activated. This is on the Merchant Facility Object.
