What are the criteria that must be included while creating Validation Rules on Payment Txn Object?
When creating validation rules always include the condition "AND( ISPICKVAL(AAkPay__Status__c,"Confirmation"), NOT(ISPICKVAL( AAkPay__Transaction_Source__c,"Recurring Payment"))" and then add your condition for validation.
Please note: This is for your information and validation rules are not covered by our standard support as they do not come delivered with the product. They are customization as per:Support Packages | Payments2Us