[Koha] Error returning a book

Hello everybody, We are having this problem when we try to return a borrowed book: "The item has not been checked in due to a configuration issue in your system." What this mean? Thanks -- *Luis Moisés Rojas P.* <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> Libre de virus. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>