64021: Pay: Invalid OperationPositive FeedbackNegative FeedbackERROR: 64021error-64021 page anchorPositive FeedbackNegative FeedbackPROGRAMMABLE VOICEERROR Descriptiondescription page anchorPositive FeedbackNegative FeedbackA 64021 Error is an indication invalid operation was provided. Possible Causespossible-causes page anchorPositive FeedbackNegative Feedback Start operation on already started Pay session Possible Solutionspossible-solutions page anchorPositive FeedbackNegative Feedback Make sure to use a valid operation