Hi, We found something very strange. use C4::Auth inside a Koha plugin brakes the CAS authentication. Looks like its a problem with "require C4::Auth_with_cas". We fixed by removing this useless dependancy. Plugin is InLibro ChangeDueDate : https://inlibro.com/koha-plugins/instructions-changeduedate/ Best regards, -- Fridolin SOMERS <fridolin.somers@biblibre.com> Software and system maintainer 🦄 BibLibre, France