The return value of getAcquirerToken in the TransactionResult class has been changed from String to byte[]. As a consequence, an application built with API 2.3.x or lower won't be able to retrieve a TransactionResult from a 2.4.x or higher service if the acquirer token field is set, and vice versa. If the Tetra transaction application set this field, ensure that the Ingenico Service Version is 2.4.1 or higher, and that your ECR application has been built using Ingenico API 2.4.1 or higher.