Braintree will throw this flag as protection against potential "carding attacks".
Usually, the rejection will be triggered when 7 or more Verifications with the same Customer Email occur within 15 minutes of each other.
Verify with the customer that the activity in your Braintree gateway is not fraudulent or if they need to contact their issuing bank.
Verify that your Risk Threshold rules are as desired.
You may review how to return to the default rules, edit rules, or add / remove rules with this helpful doc by Braintree
Once this issue is resolved, you should use the action to Restart Processing the Failed Scheduled Order.
Updated about 1 year ago